libff: Fix heap corruption caused by unnecessary av_dup_packet call

There's no need to duplicate the packet as the reference count will be 1
after the av_read_frame call. Duplicating causes heap corruption when a
synthetic clock packet is duplicated and assigned the buffer from the
stack-based temporary packet which is then double-freed by the decoder
thread.

deps/libff/libff/ff-packet-queue.c

@@ -61,10 +61,6 @@ int packet_queue_put(struct ff_packet_queue *q, struct ff_packet *packet)
 {
 	struct ff_packet_list *new_packet;
 
-	if (packet != &q->flush_packet
-			&& av_dup_packet(&packet->base) < 0)
-		return FF_PACKET_FAIL;
-
 	new_packet = av_malloc(sizeof(struct ff_packet_list));
 
 	if (new_packet == NULL)