tst_QCompleter::task178797_activedOnReturn() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ia8a81f7d00131b1a80be9fe65c3e3ed557a149d6
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/util/qcompleter/tst_qcompleter.cpp

@@ -1195,7 +1195,6 @@ void tst_QCompleter::task178797_activatedOnReturn()
     QCOMPARE(spy.size(), 0);
     ledit.move(200, 200);
     ledit.show();
-    QApplicationPrivate::setActiveWindow(&ledit);
     QVERIFY(QTest::qWaitForWindowActive(&ledit));
     QTest::keyClick(&ledit, Qt::Key_F);
     QCoreApplication::processEvents();