tst_QTooltip::qtbug64550_stylesheet() remove setActiveWindow()

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

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: I84928725fb9b6d834439aa8a64171dcf3f7a042e
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/kernel/qtooltip/tst_qtooltip.cpp

@@ -192,7 +192,6 @@ void tst_QToolTip::qtbug64550_stylesheet()
     Widget widget;
     widget.setStyleSheet(QStringLiteral("* { font-size: 48pt; }\n"));
     widget.show();
-    QApplicationPrivate::setActiveWindow(&widget);
     QVERIFY(QTest::qWaitForWindowActive(&widget));
 
     widget.showDelayedToolTip(100);