Bump third_party/openthread/repo from `f0b6fce` to `bd310db` #894

Job	Run time
Build on Linux (fake, gcc_release, clang, simulated)	2h 12m 0s
Build on Linux (gcc_debug)	1h 6m 17s
Build on Darwin (clang, python_lib, simulated)	2h 2m 21s
Build on Linux (coverage)	17m 11s
Build on Linux (python_lib)	29m 20s
Build on Linux (python lighting-app)	9m 59s
	6h 17m 8s

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