tst_QPushButton::setAccel() remove QApplicationPrivate::setActiveWindow

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ia2c79a0728a3eac5f176668c6eeb82a76b18c4b4
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/widgets/qpushbutton/tst_qpushbutton.cpp

@@ -339,7 +339,6 @@ void tst_QPushButton::setAccel()
 
     // The shortcut will not be activated unless the button is in a active
     // window and has focus
-    QApplicationPrivate::setActiveWindow(testWidget);
     testWidget->setFocus();
     QVERIFY(QTest::qWaitForWindowActive(testWidget));
     QTest::keyClick(testWidget, 'A', Qt::AltModifier);