Fix autocomplete not working on note edit form

What does this MR do?

• Fix autocomplete not working on note edit form

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

Bug introduced in https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11278

• Another MR which fixed a different case after that change, https://gitlab.com/gitlab-org/gitlab-ce/commit/e20654fcc33ad4e7df0e5da1112c33f99d4630b7, whole MR: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11322

Currently looking into the other gl.GLForm instances for regression

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 #33529 (closed)