Remove index asynchronously from merge_request_metrics
What does this MR do and why?
!141618 (merged) introduced a new combined index, that covers the same column as this index. Thus it should be removed. Sync index removal in: !142357 (merged)
!141618 (merged) introduced a new combined index, that covers the same column as this index. Thus it should be removed. Sync index removal in: !142357 (merged)