tst_QGraphicsView::update() remove QApplicationPrivate::setActiveWindow

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Id9d32ad9d346219c24e29dc5f9772ea60cf372a3
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/graphicsview/qgraphicsview/tst_qgraphicsview.cpp

@@ -4127,7 +4127,6 @@ void tst_QGraphicsView::update()
     QVERIFY(QTest::qWaitForWindowExposed(&toplevel));
 
 
-    QApplicationPrivate::setActiveWindow(&toplevel);
     QApplication::processEvents();
     QTRY_COMPARE(QApplication::activeWindow(), static_cast<QWidget *>(&toplevel));