task232085_spinBoxLineEditBg() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I8f941c2188563f72f1ff261a8d68bb0e62ae18fd
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/styles/qstylesheetstyle/tst_qstylesheetstyle.cpp

@@ -1974,7 +1974,6 @@ void tst_QStyleSheetStyle::task232085_spinBoxLineEditBg()
 
     centerOnScreen(&frame);
     frame.show();
-    QApplicationPrivate::setActiveWindow(&frame);
     spinbox->setFocus();
     QVERIFY(QTest::qWaitForWindowActive(&frame));