Animate approval icon on MR reviewers section

What does this MR do and why?

Animates approval icon in MR sidebar

Screenshots or screen recordings

Before	After

How to set up and validate locally

• Enable mr_request_changes feature flag
• Approve a merge request

✂️ UX Paper Cuts 16.7 → Project page (#430244 - closed)

✂️ UX Paper Cuts 16.8 → Accessibility (#424396 - closed)