Tests

Bump third_party/openthread/repo from `837c7fd` to `f239c49` #1416

Job	Run time
Test Suites - Linux (no-ble-tsan-clang)	1h 36m 29s
REPL Tests - Darwin	0s
REPL Tests - Linux	45m 40s
Test Suites - Darwin (no-ble-asan-clang)	1h 7m 33s
Test Suites - Darwin (no-ble-tsan-clang)	1h 51m 55s
	5h 21m 37s

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