Change the repaint() call to an update().

In show_sys(), if we directly call repaint() this
will triggers too many UpdateRequest events.
This fixes the qwidget autotest
"compatibilityChildInsertedEvents".

Reviewed-by: Richard Moe Gustavsen
(cherry picked from commit 747962e6ec20a59b7e2ed67c5cd685258f199a86)

src/gui/kernel/qwidget_mac.mm

@@ -3526,8 +3526,8 @@ void QWidgetPrivate::show_sys()
             // INVARIANT: q is native. Just show the view:
             [view setHidden:NO];
         } else {
-            // INVARIANT: q is alien. Repaint q instead:
-            q->repaint();
+            // INVARIANT: q is alien. Update q instead:
+            q->update();
         }
 #endif
     }