obs-outputs: Use correct variable for drop priority

There are two variables used for 'priority', the general marked frame
priority, and the drop priority.  They can sometimes be different
because some encoders don't always use the correct frame priority.

plugins/obs-outputs/rtmp-stream.c

@@ -905,7 +905,7 @@ static bool add_video_packet(struct rtmp_stream *stream,
 
 	/* if currently dropping frames, drop packets until it reaches the
 	 * desired priority */
-	if (packet->priority < stream->min_priority) {
+	if (packet->drop_priority < stream->min_priority) {
 		stream->dropped_frames++;
 		return false;
 	} else {