Tests

Bump third_party/openthread/repo from `2aeb8b8` to `b8d2e5d` #394

Job	Run time
REPL Tests - Darwin	0s
REPL Tests - Linux	1h 33m 55s
Test Suites - Darwin (no-ble-no-shell-asan-clang)	1h 35m 20s
Test Suites - Darwin (no-ble-no-shell-tsan-clang)	1h 53m 0s
Test Suites - Linux (no-ble-no-shell-tsan-clang)	2h 0m 56s
	7h 3m 11s

Provide feedback