Bump third_party/openthread/repo from `aed9cd1` to `c519aa4` #340

Job	Run time
Unit / Integration Tests (main)	15m 57s
Unit / Integration Tests (clang)	16m 45s
Unit / Integration Tests (mbedtls)	16m 50s
Unit / Integration Tests (rotating_device_id)	16m 2s
Unit / Integration Tests (icd)	45m 7s
	1h 50m 41s

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