Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/33868

While in a MR "Changes" tab looking at some diff note discussions.
Clicking reply and pressing the up-arrow should edit your last comment in
that discussion.

I suspect this regressed in
https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11173/diffs#f4bb984ec495c5cb58516785c62978f5209c39b4_179_178
where we changed the selector