Fix issues filter selection

What does this MR do?

When a user selects and de-selects multiple items from the issue label filter dropdown, the title on the dropdown can fall out of sync such that the title no longer matches what is currently selected.

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

I did not find any documentation on front end tests. Just wanted to check if I was missing anything as this is my first MR to GitLab.

Why was this MR needed?

This resolves a UI bug found on the latest master branch and gitlab.com

What are the relevant issue numbers?

Closes #20037 (closed)

Does this MR meet the acceptance criteria?

• CHANGELOG entry added
• Tests
  • Added tests
  • All builds are passing
• Conform by the style guides
• Branch has no merge conflicts with master (if you do - rebase it please)
• Squashed related commits together