tst_QTreeView::keyboardSearchMultiColumn() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I1ca04abbb1f67d5a4a6157725891a4a076abfe75
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/itemviews/qtreeview/tst_qtreeview.cpp

@@ -1240,7 +1240,6 @@ void tst_QTreeView::keyboardSearchMultiColumn()
 
     view.setModel(&model);
     view.show();
-    QApplicationPrivate::setActiveWindow(&view);
     QVERIFY(QTest::qWaitForWindowActive(&view));
 
     view.setCurrentIndex(model.index(0, 1));