tst_QGraphicsItem::focusHandling() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I96335a24c40444d09e5069898b6bd49499550156
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/graphicsview/qgraphicsitem/tst_qgraphicsitem.cpp

@@ -10927,7 +10927,6 @@ void tst_QGraphicsItem::focusHandling()
     view.show();
     QVERIFY(QTest::qWaitForWindowExposed(&view));
 
-    QApplicationPrivate::setActiveWindow(&view);
     QTRY_COMPARE(QApplication::activeWindow(), static_cast<QWidget *>(&view));
     QVERIFY(itemWithFocus->hasFocus());