in_systemd: remove unreferenced field from flb_systemd_config

[chitoku-k]

This PR removes a field that has no longer been referenced since #9773.

---

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Testing
Before we can approve your change; please submit the following in a comment:

• Example configuration file for the change
• Debug log output from testing the change

• Attached Valgrind output that shows no leaks or memory corruption was found

If this is a change to packaging of containers or native binaries then please confirm it works for all targets.

• [N/A] Run local packaging test showing all targets (including any new ones) build.
• [N/A] Set ok-package-test label to test for all targets (requires maintainer to do).

Documentation

• [N/A] Documentation required for this feature

Backporting

• Backport to latest stable release.

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Fluent Bit is licensed under Apache 2.0, by submitting this pull request I understand that this code will be released under the terms of that license.

[chitoku-k]

Config

[SERVICE]
    Parsers_File    parsers.conf

[INPUT]
    Name            systemd
    Systemd_Filter  _SYSTEMD_UNIT=systemd-logind.service
    Read_From_Tail  On
    Lowercase       On

[OUTPUT]
    Name            stdout
    Match           *

[FILTER]
    Name            parser
    Match           *
    Key_Name        message
    Parser          json

Log

$ bin/fluent-bit -c config
Fluent Bit v3.2.4
* Copyright (C) 2015-2024 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

______ _                  _    ______ _ _           _____  _____
|  ___| |                | |   | ___ (_) |         |____ |/ __  \
| |_  | |_   _  ___ _ __ | |_  | |_/ /_| |_  __   __   / /`' / /'
|  _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / /   \ \  / /
| |   | | |_| |  __/ | | | |_  | |_/ / | |_   \ V /.___/ /./ /___
\_|   |_|\__,_|\___|_| |_|\__| \____/|_|\__|   \_/ \____(_)_____/


[2024/12/31 14:45:23] [ info] [fluent bit] version=3.2.4, commit=40e59d17df, pid=867569
[2024/12/31 14:45:23] [ info] [storage] ver=1.1.6, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2024/12/31 14:45:23] [ info] [simd    ] disabled
[2024/12/31 14:45:23] [ info] [cmetrics] version=0.9.9
[2024/12/31 14:45:23] [ info] [ctraces ] version=0.5.7
[2024/12/31 14:45:23] [ info] [input:systemd:systemd.0] initializing
[2024/12/31 14:45:23] [ info] [input:systemd:systemd.0] storage_strategy='memory' (memory only)
[2024/12/31 14:45:23] [ info] [sp] stream processor started
[2024/12/31 14:45:23] [ info] [output:stdout:stdout.0] worker #0 started
[0] systemd.0: [[1735623925.952662000, {}], {"priority"=>"6", "_transport"=>"journal", "_systemd_slice"=>"system.slice", "_boot_id"=>"13b17aa502d94c34a4e1865f76a65813", "_machine_id"=>"09cb1f91a4af4686bc1b57cad2710c32", "_hostname"=>"lychee", "_runtime_scope"=>"system", "_uid"=>"0", "_gid"=>"0", "syslog_facility"=>"4", "tid"=>"531", "code_file"=>"src/login/logind-session.c", "code_line"=>"854", "code_func"=>"session_start", "syslog_identifier"=>"systemd-logind", "message_id"=>"8d45620c1a4348dbb17410da57c60c66", "user_id"=>"chitoku", "_pid"=>"531", "_comm"=>"systemd-logind", "_exe"=>"/usr/lib/systemd/systemd-logind", "_cmdline"=>"/usr/lib/systemd/systemd-logind", "_cap_effective"=>"24420020f", "_systemd_cgroup"=>"/system.slice/systemd-logind.service", "_systemd_unit"=>"systemd-logind.service", "_systemd_invocation_id"=>"85d456458dd14c7789187fccf9e5f38b", "session_id"=>"19", "leader"=>"867592", "message"=>"New session 19 of user chitoku.", "_source_realtime_timestamp"=>"1735623925952519"}]
^C[2024/12/31 14:45:34] [engine] caught signal (SIGINT)
[2024/12/31 14:45:34] [ warn] [engine] service will shutdown in max 5 seconds
[2024/12/31 14:45:34] [ info] [input] pausing systemd.0
[2024/12/31 14:45:34] [ info] [engine] service has stopped (0 pending tasks)
[2024/12/31 14:45:34] [ info] [input] pausing systemd.0
[2024/12/31 14:45:34] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2024/12/31 14:45:34] [ info] [output:stdout:stdout.0] thread worker #0 stopped

Valgrind output

$ valgrind --leak-check=full bin/fluent-bit -c config
==867889== Memcheck, a memory error detector
==867889== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==867889== Using Valgrind-3.24.0 and LibVEX; rerun with -h for copyright info
==867889== Command: bin/fluent-bit -c config
==867889==
Fluent Bit v3.2.4
* Copyright (C) 2015-2024 The Fluent Bit Authors
* Fluent Bit is a CNCF sub-project under the umbrella of Fluentd
* https://fluentbit.io

______ _                  _    ______ _ _           _____  _____
|  ___| |                | |   | ___ (_) |         |____ |/ __  \
| |_  | |_   _  ___ _ __ | |_  | |_/ /_| |_  __   __   / /`' / /'
|  _| | | | | |/ _ \ '_ \| __| | ___ \ | __| \ \ / /   \ \  / /
| |   | | |_| |  __/ | | | |_  | |_/ / | |_   \ V /.___/ /./ /___
\_|   |_|\__,_|\___|_| |_|\__| \____/|_|\__|   \_/ \____(_)_____/


[2024/12/31 14:46:03] [ info] [fluent bit] version=3.2.4, commit=40e59d17df, pid=867889
[2024/12/31 14:46:03] [ info] [storage] ver=1.1.6, type=memory, sync=normal, checksum=off, max_chunks_up=128
[2024/12/31 14:46:03] [ info] [simd    ] disabled
[2024/12/31 14:46:03] [ info] [cmetrics] version=0.9.9
[2024/12/31 14:46:03] [ info] [ctraces ] version=0.5.7
[2024/12/31 14:46:03] [ info] [input:systemd:systemd.0] initializing
[2024/12/31 14:46:06] [ info] [output:stdout:stdout.0] worker #0 started
[2024/12/31 14:46:03] [ info] [input:systemd:systemd.0] storage_strategy='memory' (memory only)
[2024/12/31 14:46:06] [ info] [sp] stream processor started
[0] systemd.0: [[1735623981.184742000, {}], {"priority"=>"6", "_transport"=>"journal", "_systemd_slice"=>"system.slice", "_boot_id"=>"13b17aa502d94c34a4e1865f76a65813", "_machine_id"=>"09cb1f91a4af4686bc1b57cad2710c32", "_hostname"=>"lychee", "_runtime_scope"=>"system", "_uid"=>"0", "_gid"=>"0", "syslog_facility"=>"4", "tid"=>"531", "code_file"=>"src/login/logind-session.c", "code_line"=>"854", "code_func"=>"session_start", "syslog_identifier"=>"systemd-logind", "message_id"=>"8d45620c1a4348dbb17410da57c60c66", "user_id"=>"chitoku", "_pid"=>"531", "_comm"=>"systemd-logind", "_exe"=>"/usr/lib/systemd/systemd-logind", "_cmdline"=>"/usr/lib/systemd/systemd-logind", "_cap_effective"=>"24420020f", "_systemd_cgroup"=>"/system.slice/systemd-logind.service", "_systemd_unit"=>"systemd-logind.service", "_systemd_invocation_id"=>"85d456458dd14c7789187fccf9e5f38b", "session_id"=>"20", "leader"=>"868066", "message"=>"New session 20 of user chitoku.", "_source_realtime_timestamp"=>"1735623981184674"}]
^C[2024/12/31 14:46:27] [engine] caught signal (SIGINT)
[2024/12/31 14:46:27] [ warn] [engine] service will shutdown in max 5 seconds
[2024/12/31 14:46:27] [ info] [input] pausing systemd.0
[2024/12/31 14:46:27] [ info] [engine] service has stopped (0 pending tasks)
[2024/12/31 14:46:27] [ info] [input] pausing systemd.0
[2024/12/31 14:46:27] [ info] [output:stdout:stdout.0] thread worker #0 stopping...
[2024/12/31 14:46:27] [ info] [output:stdout:stdout.0] thread worker #0 stopped
==867889==
==867889== HEAP SUMMARY:
==867889==     in use at exit: 0 bytes in 0 blocks
==867889==   total heap usage: 3,080 allocs, 3,080 frees, 1,859,754 bytes allocated
==867889==
==867889== All heap blocks were freed -- no leaks are possible
==867889==
==867889== For lists of detected and suppressed errors, rerun with: -s
==867889== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)