Remove mEnterAnimationPending check for accessibility

Accessibility was relying on WS.mEnterAnimationPending to determine if a
window was ready on screen. However, that variable no longer represents
what it used to and it doesn't actually mean the app is animating. The
variable is only set when a relayout is requested and then unset when
show is called. Accessibility is already checking isOnScreen and
isVisibleLw so that should cover the cases to check if the window is
ready.

mEnterAnimationPending is not always set properly and causes issues with
accessibility, which is the only place currently using it.

Fixes: 152537982
Test: Magnification for Accessibility works
Change-Id: Ib0f37b3cc6d744fd84f466a65e6ce006e07e116e