tst_QGraphicsScene::hoverEvents_siblings() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ic1447c4ed8cd33a96fedf775abb363cc99b347d6
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/graphicsview/qgraphicsscene/tst_qgraphicsscene.cpp

@@ -1601,7 +1601,6 @@ void tst_QGraphicsScene::hoverEvents_siblings()
     view.rotate(10);
     view.scale(1.7, 1.7);
     view.show();
-    QApplicationPrivate::setActiveWindow(&view);
     view.activateWindow();
     QVERIFY(QTest::qWaitForWindowActive(&view));