Remove canStartRecentsAnimation logics

Since we won't cancel recent animation during task switching as we
still keeps the connection to reparent the new task animation target
with onTaskAppeared, so we don't need to care about the next recents
animation starts timing if the next task transition is set.

Bug: 152480470
Test: swipe to next task, see if any flickring when swipped.
Change-Id: I5abfbefa9b05751b08c2b235609270977ae55292