tst_QWidget::scroll() remove QApplicationPrivate::setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I13ea8c0994eaeb764462af23ef66ea1a37659b77
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

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

@@ -5877,7 +5877,6 @@ void tst_QWidget::scroll()
     updateWidget.reset();
     updateWidget.move(m_availableTopLeft);
     updateWidget.showNormal();
-    QApplicationPrivate::setActiveWindow(&updateWidget);
     QVERIFY(QTest::qWaitForWindowActive(&updateWidget));
     QVERIFY(updateWidget.numPaintEvents > 0);