UV pin: Use ID_RECALC_COPY_ON_WRITE instead of the almighty 0

I suppose the cow tag is more correct for those generic/non-specific
tags. Thank you Sergey.

source/blender/editors/uvedit/uvedit_ops.c

@@ -3969,7 +3969,7 @@ static int uv_pin_exec(bContext *C, wmOperator *op)
 
 		if (changed) {
 			WM_event_add_notifier(C, NC_GEOM | ND_DATA, obedit->data);
-			DEG_id_tag_update(obedit->data, 0);
+			DEG_id_tag_update(obedit->data, ID_RECALC_COPY_ON_WRITE);
 		}
 	}
 	MEM_freeN(objects);