tst_QWidget::enterLeaveOnWindowShowHide() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ic189b1c55b6bdf0397636b3ae9555cc38b60fc48
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

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

@@ -10900,7 +10900,6 @@ void tst_QWidget::enterLeaveOnWindowShowHide()
     if (!QTest::qWaitFor([&]{ return widget.geometry().contains(QCursor::pos()); }))
         QSKIP("We can't move the cursor");
     widget.show();
-    QApplicationPrivate::setActiveWindow(&widget);
     QVERIFY(QTest::qWaitForWindowActive(&widget));
 
     ++expectedEnter;