tst_QTextBrowser::TextBrowser() remove setActiveWindow()

2f6fe3a26843ff68c5d3f9af0a2fc3cce6caac22 as made calls to
QApplicationPrivate::setActiveWindow() redundant.

Remove redundant calls.

Task-number: QTBUG-121488
Change-Id: Ia006f35177f3c8b2cb3d7b8c6bbe3f24eb24d934
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>

tests/auto/widgets/widgets/qtextbrowser/tst_qtextbrowser.cpp

@@ -19,7 +19,6 @@ class TestBrowser : public QTextBrowser
 public:
     inline TestBrowser() {
         show();
-        QApplicationPrivate::setActiveWindow(this);
         activateWindow();
         setFocus();
         QVERIFY(QTest::qWaitForWindowActive(this));