Tests

Bump third_party/openthread/repo from `287dbfa` to `971f05f` #352

Job	Run time
REPL Tests - Darwin	0s
REPL Tests - Linux	1h 41m 29s
Test Suites - Linux (no-ble-no-shell-tsan-clang)	1h 48m 48s
Test Suites - Darwin (no-ble-no-shell-asan-clang)	1h 40m 24s
Test Suites - Darwin (no-ble-no-shell-tsan-clang)	1h 53m 43s
	7h 4m 24s

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