Bump third_party/ot-br-posix/repo from `bd15f71` to `722f283` #434

Job	Run time
Build on Darwin (clang, simulated)	53m 31s
Build on Linux (fake, gcc_release, clang, simulated)	51m 9s
Build on Linux (coverage)	15m 5s
Build on Linux (gcc_debug)	1h 5m 56s
Build on Linux (python_lib)	24m 45s
Build on Linux (python lighting-app)	7m 51s
	3h 38m 17s

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