Remove transition listener in MultiListener and FragmentTransition

Found two places where we forgot to remove TransitionListener in onTransitionEnd. I think it is important to clear it as if you reuse a transition object it will be leaked together with some views

Test: n/a
Bug: 64643817
Fixes in AndroidX: aosp/793641, aosp/795753

Change-Id: Iae0a9945a4158776f1a75c806c1f29efc049f96b