tst_QWidget::tabOrderWithCompoundWidgets() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: If805bc0e021625b94edc83d7abccc435c1880bea
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

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

@@ -2439,7 +2439,6 @@ void tst_QWidget::tabOrderWithCompoundWidgets()
 
     container.show();
     container.activateWindow();
-    QApplicationPrivate::setActiveWindow(&container);
     QVERIFY(QTest::qWaitForWindowActive(&container));
 
     lastEdit->setFocus();