Bump third_party/ot-br-posix/repo from `8299da3` to `69ce2a5` #4666

Job	Run time
Unit / Integration Tests (main)	19m 12s
Unit / Integration Tests (clang)	18m 46s
Unit / Integration Tests (mbedtls)	22m 28s
Unit / Integration Tests (rotating_device_id)	24m 56s
	1h 25m 22s

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