Investigate FindCommit performance on Gitaly cny

Gitaly canary has an active alert silence: #619 (closed)

We can see from this query that the biggest spikes currently are from FindCommit:

This is not because FindCommit is slower overall on canary. The tail latency on main is actually higher https://log.gprd.gitlab.net/goto/e04f44c026f6c5affc439bebdb1b01f3:

The problem appears to be that on canary, because it contains our repos, the distribution of timings is different. We should investigate why that is and fix it if possible. (Maybe an N+1 in the application?)