tst_QFileDialog::focus() remove QApplicationPrivate::setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ie48dd98fa8eae796e31de3afc34e09c27e3b78cd
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/dialogs/qfiledialog/tst_qfiledialog.cpp

@@ -1117,7 +1117,6 @@ void tst_QFiledialog::focus()
     QFileDialog fd;
     fd.setDirectory(QDir::currentPath());
     fd.show();
-    QApplicationPrivate::setActiveWindow(&fd);
     QVERIFY(QTest::qWaitForWindowActive(&fd));
     QCOMPARE(fd.isVisible(), true);
     QCOMPARE(QApplication::activeWindow(), static_cast<QWidget*>(&fd));