tst_QGraphicsWidget::setTabOrder_data() remove setActiveWindow()

2f6fe3a268 has made calls to
QApplicationPrivate::setActiveWindow() redundant.

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: If105d1c2db3646c7d31d72aeaa373015f175fd44
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/graphicsview/qgraphicswidget/tst_qgraphicswidget.cpp

@@ -1388,7 +1388,6 @@ void tst_QGraphicsWidget::setTabOrder()
     QGraphicsScene scene;
     QGraphicsView view(&scene);
     view.show();
-    QApplicationPrivate::setActiveWindow(&view);
     QVERIFY(QTest::qWaitForWindowActive(&view));
 
     QGraphicsWidget *lastItem = nullptr;