Bump third_party/nanopb/repo from `671672b` to `8e9d5a1` #2301

Job	Run time
Build Docker CHIP Build images - base	5m 13s
Build Docker CHIP Build images - base (-minimal)	40s
Build Docker CHIP Build images - stage 1 (-crosscompile)	57s
Build Docker CHIP Build images - stage 2 (-ameba)	1m 59s
Build Docker CHIP Build images - stage 2 (-asr)	1m 1s
Build Docker CHIP Build images - stage 2 (-bouffalolab)	1h 13m 44s
Build Docker CHIP Build images - stage 2 (-doxygen)	13s
Build Docker CHIP Build images - stage 2 (-efr32)	1m 36s
Build Docker CHIP Build images - stage 2 (-esp32)	2m 19s
Build Docker CHIP Build images - stage 2 (-infineon)	2m 6s
Build Docker CHIP Build images - stage 2 (-java)	46s
Build Docker CHIP Build images - stage 2 (-nxp)	5m 19s
Build Docker CHIP Build images - stage 2 (-nxp-zephyr)	2m 33s
Build Docker CHIP Build images - stage 2 (-nrf-platform)	4m 4s
Build Docker CHIP Build images - stage 2 (-telink)	4m 29s
Build Docker CHIP Build images - stage 2 (-telink-zephyr_3_3)	3m 54s
Build Docker CHIP Build images - stage 2 (-ti)	54s
Build Docker CHIP Build images - stage 2 (-tizen)	1m 57s
Build Docker CHIP Build images - stage 2 (-openiotsdk)	58s
Build Docker CHIP Build images - stage 3 (-android)	2m 57s
Build Docker CHIP Build images - stage 3 (-esp32-qemu)	3m 13s
Build Docker CHIP Build images - stage 3 (-tizen-qemu)	16m 48s
Build Docker CHIP Build images - vscode	0s
	2h 17m 40s

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