Fix pressing up-arrow on a MR "Changes" diff discussion edits your last note

What does this MR do?

Fix pressing up-arrow on a MR "Changes" diff discussion edits your last note.

Are there points in the code the reviewer needs to double check?

I suspect this regressed in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11173/diffs#f4bb984ec495c5cb58516785c62978f5209c39b4_179_178 where we changed the selector to be more specific on where it looks.

Why was this MR needed?

Pressing up-arrow on a MR "Changes" diff discussion didn't do anything.

Does this MR meet the acceptance criteria?

• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #33868 (closed)