QTBUG6407_extendedSelection() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I073cbf74f11c3492444ecd94655e6b1e4e75611d
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/itemviews/qabstractitemview/tst_qabstractitemview.cpp

@@ -1557,7 +1557,6 @@ void tst_QAbstractItemView::QTBUG6407_extendedSelection()
     moveCursorAway(&view);
 
     view.show();
-    QApplicationPrivate::setActiveWindow(&view);
     QVERIFY(QTest::qWaitForWindowActive(&view));
     QCOMPARE(&view, QApplication::activeWindow());