Fix filtering of milestones with quotes in title

What does this MR do?

Fixes #23268 (closed).

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

GitLabDropdown seem to be used in many places. Be careful when reviewing it. BTW the same "escaping" is used here.

Why was this MR needed?

It wasn't possible to filter by milestones when at least 1 milestone had ' in it's name since JS was throwing an exception. This MR fixes the bug.

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Documentation created/updated
• API support added
• 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 #23268 (closed)