tst_QWidget::focusChainOnHide remove QApplicationPrivate::setActiveWind

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I5b429dcaa47cd179785345f9f7a80648574670dd
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

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

@@ -1937,8 +1937,6 @@ void tst_QWidget::focusChainOnHide()
     QWidget::setTabOrder(child, parent.data());
 
     parent->show();
-    QApplicationPrivate::setActiveWindow(parent->window());
-    child->activateWindow();
     child->setFocus();
 
     QTRY_VERIFY(child->hasFocus());