Updates A11y Shortcut animations to not loop in code.

Continuously repeated animations go against accessibility guidelines
to avoid unstoppable motion.

The animation files themselves have been updated to loop twice
so that the user can still see the animation temporarily.
The loop restarts if the user exits and enters the page again.

Bug: 370661517
Flag: EXEMPT minor bugfix with resource changes
Test: Manually observe animations
Change-Id: I52348a094680ef345bf8c2b12ab91c9406bf5cb4