tst_QTreeView::keyboardNavigationWithDisabled remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I1abfd397f74fe8ce5fb37c3ea7128e4e577e717e
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp

@@ -4179,7 +4179,6 @@ void tst_QTreeView::keyboardNavigationWithDisabled()
 
     view.resize(200, view.visualRect(model.index(0,0)).height()*10);
     topLevel.show();
-    QApplicationPrivate::setActiveWindow(&topLevel);
     QVERIFY(QTest::qWaitForWindowActive(&topLevel));
     QVERIFY(topLevel.isActiveWindow());