tst_QMenuBar::taskQTBUG56860_focus() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I96178f118ab5d60d23047a01c884a9cddcf213d5
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/widgets/qmenubar/tst_qmenubar.cpp

@@ -745,7 +745,6 @@ void tst_QMenuBar::taskQTBUG56860_focus()
 
     w.setCentralWidget(e);
     w.show();
-    QApplicationPrivate::setActiveWindow(&w);
     QVERIFY(QTest::qWaitForWindowActive(&w));
 
     QTRY_COMPARE(QApplication::focusWidget(), e);