QmlDesigner: Fix StateEditor show event update

Task-number: QDS-2798
Change-Id: Ic27e7491012b227e144cdae68ead8ac534cc0d5a
Reviewed-by: Thomas Hartmann <thomas.hartmann@qt.io>

src/plugins/qmldesigner/components/stateseditor/stateseditorwidget.cpp

@@ -132,7 +132,7 @@ void StatesEditorWidget::toggleStatesViewExpanded()
 
 void StatesEditorWidget::showEvent(QShowEvent *event)
 {
-    Q_UNUSED(event)
+    QQuickWidget::showEvent(event);
     update();
 }