In one example, we found
`Projects::MergeRequests::DiffsController#diffs_metadata` calling Gitaly
over 3000 times with the same ref name for FindCommit. Since all actions
in this controller are GET requests, it should be safe to enable this
for all actions inside `DiffsController`, just as we do with
`CommitsController`.

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/217192