Bump third_party/pigweed/repo from `9504c03` to `8b5d45a` #1126

Job	Run time
Build on Linux (fake, gcc_release, clang, simulated)	3m 2s
Build on Linux (gcc_debug)	3m 3s
Build on Linux (python_lib)	2m 24s
Build on Linux (python lighting-app)	2m 47s
Build on Linux (coverage)	2m 30s
Build on Darwin (clang, python_lib, simulated)	3m 33s
	17m 19s

Provide feedback