RingtoneManager: allow video ringtone URI

When checking the MIME type for the default ringtone, also
allow it to refer to video content.

Bug: 205837340
Test: see POC + atest android.media.audio.cts.RingtoneManagerTest
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:de83ef4f51cad7ea1eb91f5d328d79b719251abe)
Merged-In: Iac9f27f14bae29e0fabc31e05da2357f6f4f16c7
Change-Id: Iac9f27f14bae29e0fabc31e05da2357f6f4f16c7