Bump third_party/ot-br-posix/repo from `bd15f71` to `722f283` #434

Job	Run time
Unit / Integration Tests (main)	16m 6s
Unit / Integration Tests (clang)	16m 59s
Unit / Integration Tests (mbedtls)	16m 11s
Unit / Integration Tests (rotating_device_id)	16m 37s
Unit / Integration Tests (icd)	46m 20s
	1h 52m 13s

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