Remove WindowContainer.AnimationFlags.TRANSITION

The animation type is no longer used since legacy app transition
was removed.

Also remove deprecated isAnimating(int flags) which is replaced by
isAnimating(flags, ANIMATION_TYPE_ALL).

Bug: 365884835
Flag: EXEMPT remove dead code
Test: WindowContainerTests

Change-Id: Ida822c149bdfdd3b722e8d441f233a0f43159621