Clamp scrim progress for slow taskbar animation duration to max 1f

* Overview to workspace taskbar animation changed duration, and
with the new longer duration we no longer need to speed up the
scrim animation.
* The new longer duration was actually slowing down the scrim
interpolator

Fixes: 351911299
Test: Tested on small and large screen.
Tested w/ the flag off and there is a flicker, but that was
present without these changes as well
Flag: EXEMPT bugfix

Change-Id: I5dc219de541f3c2fb29a5a91a4770b0dece0259e