Make gif test less flaky

[davepagurek]

Resolves #6089

Changes:

• Before, this test waited 100ms for a gif to go to the next frame, plus a bit extra to wait for a draw to happen
• However, the draw doesn't reliably happen in that extra 10ms, causing tests to fail occasionally
• Now it explicitly waits for the next frame instead of adding a bit of extra time to the timeout

Screenshots of the change:
N/A

PR Checklist

• npm run lint passes
• [Inline documentation] is included / updated
• [Unit tests] are included / updated

[limzykenneth]

I did notice this behaviour as well the other day, I think this fix should work as long as in the previous 100ms wait the gif has moved to the next frame. You can merge this when ready.