Delete code used to read content:// URIs from MediaPlayerService

All valid content:// URIs are resolved in MediaPlayer.java before
the binder call into the mediaserver process. Trying to resolve a
content:// URI from this process fails with the following error:

E ActivityManager: Cannot find package for uid: 1013

Since it's not possible to resolve content:// URIs from here, we can
delete this code.

Bug: 236688380
Test: atest MediaPlayerTest
Change-Id: I690aca747429b7b976887069a0a497589307a497