video_output: a crop event is not an error

Lower the log level

src/video_output/video_output.c

@@ -1391,7 +1391,7 @@ static void ThreadExecuteCropBorder(vout_thread_t *vout,
                                     unsigned left, unsigned top,
                                     unsigned right, unsigned bottom)
 {
-    msg_Err(vout, "ThreadExecuteCropBorder %d.%d %dx%d", left, top, right, bottom);
+    msg_Dbg(vout, "ThreadExecuteCropBorder %d.%d %dx%d", left, top, right, bottom);
     vout_SetDisplayCrop(vout->p->display.vd, 0, 0,
                         left, top, -(int)right, -(int)bottom);
 }