Remove bad finalizer from Ringtone.

This should have moved to LocalRingtonePlayer, but I don't see why the
finalizer is needed at all: the MediaPlayer's finalizer should do its
own thing (orig intro bug 11366759 was about too-eager release).

Bug: 271905784
Test: presubmit
Change-Id: Iff84f413111cf62e727745e84d90579c22666702