ffplay: replace use of av_copy_packet()

Signed-off-by: James Almer <jamrial@gmail.com>

ffplay.c

@@ -2978,7 +2978,7 @@ static int read_thread(void *arg)
         if (is->queue_attachments_req) {
             if (is->video_st && is->video_st->disposition & AV_DISPOSITION_ATTACHED_PIC) {
                 AVPacket copy = { 0 };
-                if ((ret = av_copy_packet(&copy, &is->video_st->attached_pic)) < 0)
+                if ((ret = av_packet_ref(&copy, &is->video_st->attached_pic)) < 0)
                     goto fail;
                 packet_queue_put(&is->videoq, &copy);
                 packet_queue_put_nullpacket(&is->videoq, is->video_stream);