Bump third_party/pigweed/repo from `ce0e3e2` to `4bf11f1` #994

Job	Run time
Build on Darwin (clang, simulated)	3m 47s
Build on Linux (fake, gcc_release, clang, simulated)	3m 31s
Build on Linux (coverage)	1m 58s
Build on Linux (gcc_debug)	3m 20s
Build on Linux (python_lib)	2m 9s
Build on Linux (python lighting-app)	2m 25s
	17m 10s

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