Bump third_party/nanopb/repo from `671672b` to `8e9d5a1` #2289

Job	Run time
Build Docker CHIP Build images - base	5m 12s
Build Docker CHIP Build images - base (-minimal)	39s
Build Docker CHIP Build images - stage 1 (-crosscompile)	58s
Build Docker CHIP Build images - stage 2 (-ameba)	1m 58s
Build Docker CHIP Build images - stage 2 (-asr)	1m 0s
Build Docker CHIP Build images - stage 2 (-bouffalolab)	25m 55s
Build Docker CHIP Build images - stage 2 (-doxygen)	14s
Build Docker CHIP Build images - stage 2 (-efr32)	1m 35s
Build Docker CHIP Build images - stage 2 (-esp32)	2m 4s
Build Docker CHIP Build images - stage 2 (-infineon)	1m 59s
Build Docker CHIP Build images - stage 2 (-java)	58s
Build Docker CHIP Build images - stage 2 (-nxp)	4m 54s
Build Docker CHIP Build images - stage 2 (-nxp-zephyr)	2m 35s
Build Docker CHIP Build images - stage 2 (-nrf-platform)	3m 42s
Build Docker CHIP Build images - stage 2 (-telink)	4m 36s
Build Docker CHIP Build images - stage 2 (-ti)	48s
Build Docker CHIP Build images - stage 2 (-tizen)	1m 57s
Build Docker CHIP Build images - stage 2 (-openiotsdk)	1m 4s
Build Docker CHIP Build images - stage 3 (-android)	2m 52s
Build Docker CHIP Build images - stage 3 (-esp32-qemu)	3m 13s
Build Docker CHIP Build images - stage 3 (-tizen-qemu)	15m 46s
Build Docker CHIP Build images - vscode	0s
	1h 23m 59s

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