Tests

Bump third_party/openthread/repo from `2aeb8b8` to `b42be4c` #312

Job	Run time
REPL Tests - Darwin	0s
REPL Tests - Linux	1h 33m 53s
Test Suites - Darwin (no-ble-asan-clang)	1h 32m 1s
Test Suites - Linux (no-ble-tsan-clang)	1h 48m 40s
Test Suites - Darwin (no-ble-tsan-clang)	2h 4m 10s
	6h 58m 44s

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