pl_Get(): remove VLC_USED qualifier

pl_Get() does not create a reference to the playlist, so nothing is
leaked if the result is ignored. Calling pl_Get() ensures that the
playlist has been created.

include/vlc_playlist.h

@@ -251,7 +251,7 @@ enum pl_locked_state
 #define PL_UNLOCK playlist_Unlock( p_playlist )
 #define PL_ASSERT_LOCKED playlist_AssertLocked( p_playlist )
 
-VLC_API playlist_t * pl_Get( vlc_object_t * ) VLC_USED;
+VLC_API playlist_t * pl_Get( vlc_object_t * );
 #define pl_Get( a ) pl_Get( VLC_OBJECT(a) )
 
 /* Playlist control */