tst_QHeaderview::focusPolicy() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ie2be1421019d09d12d1860b22fe1c98fd8bc2a59
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/itemviews/qheaderview/tst_qheaderview.cpp

@@ -1620,7 +1620,6 @@ void tst_QHeaderView::focusPolicy()
 
     widget.show();
     widget.setFocus(Qt::OtherFocusReason);
-    QApplicationPrivate::setActiveWindow(&widget);
     widget.activateWindow();
     QVERIFY(QTest::qWaitForWindowActive(&widget));
     QVERIFY(widget.hasFocus());