tst_QDateTimeEdit::enterKey remove QApplicationPrivate::setActiveWindow

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I948165217193a6616828475682c7d75f057b3f39
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/widgets/qdatetimeedit/tst_qdatetimeedit.cpp

@@ -1064,7 +1064,6 @@ void tst_QDateTimeEdit::tabKeyNavigationWithSuffix()
 
 void tst_QDateTimeEdit::enterKey()
 {
-    QApplicationPrivate::setActiveWindow(testWidget);
     testWidget->setDate(QDate(2004, 5, 11));
     testWidget->setDisplayFormat("prefix d/MM/yyyy 'suffix'");
     testWidget->lineEdit()->setFocus();