Bump third_party/ot-br-posix/repo from `bd15f71` to `d4fa5d3` #2335

Job	Run time
Build on Linux (fake, gcc_release, clang, simulated)	2h 10m 58s
Build on Linux (gcc_debug)	1h 14m 55s
Build on Linux (python_lib)	32m 55s
Build on Darwin (clang, python_lib, simulated)	1h 59m 54s
Build on Linux (coverage)	17m 1s
Build on Linux (python lighting-app)	6m 44s
	6h 22m 27s

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