tst_QWidget::reverseTabOrder remove QApplicationPrivate::setActiveWindo

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ifd2c5dcd1cc3d13f689ffd6400ffec0fcc3a6b93
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/kernel/qwidget/tst_qwidget.cpp

@@ -2105,7 +2105,6 @@ void tst_QWidget::reverseTabOrder()
 
     container.show();
     container.activateWindow();
-    QApplicationPrivate::setActiveWindow(&container);
     QVERIFY(QTest::qWaitForWindowActive(&container));
 
     QTRY_VERIFY(firstEdit->hasFocus());