callbacks: Remove on_pq_track_deleted()

It's been replaced with a function in the QNotifier class.

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>

core/callback.cpp

@@ -12,7 +12,6 @@ static void no_op(Queue *) {}
 static struct Callbacks callbacks = {
 	.on_pq_removed			= no_op,
 
-	.on_queue_track_del		= no_op,
 	.on_queue_track_changed		= no_op,
 };
 

core/queue.cpp

@@ -166,7 +166,6 @@ void Queue :: del(unsigned int index)
 	_length -= _tracks[index]->length();
 	_tracks.erase(_tracks.begin() + index);
 	_notify->on_track_removed(index);
-	get_callbacks()->on_queue_track_del(this, index);
 }
 
 void Queue :: del(Track *track)

include/core/callback.h

@@ -24,14 +24,6 @@ struct Callbacks {
 
 	/* Queue callbacks */
 
-	/**
-	 * Called when tracks are removed from a queue
-	 *
-	 * @param  queue  The queue that was just modified.
-	 * @param  row    The former index of the track.
-	 */
-	void (*on_queue_track_del)(Queue *, unsigned int);
-
 	/**
 	 * Called when a track's metadata changes.
 	 *