Reduce footprint of animate.js

What does this MR do?

Removes the animate.js utility, and removes the one place it was being used: the issuable sidebar label animation.

Why was this MR needed?

The animate.js file was made up of a lot of unused code that's currently getting loaded on every page, and the labels animation is the only one of its kind in GitLab. We're knocking about 1KB off of our main js file.

Screenshots (if relevant)

With:

Without:

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary

• Review

  • Has been reviewed by UX
  • Has been reviewed by Frontend

What are the relevant issue numbers?