Bump third_party/openthread/repo from `2aeb8b8` to `ada03e6` #5566

Job	Run time
Build on Darwin (clang, simulated)	46m 43s
Build on Linux (fake, gcc_release, clang, simulated)	51m 41s
Build on Linux (coverage)	15m 46s
Build on Linux (gcc_debug)	1h 5m 26s
Build on Linux (python_lib)	23m 12s
Build on Linux (python lighting-app)	6m 19s
	3h 29m 7s

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