tst_QGestureRecognizer::swipeGesture set FramelessWindowHint

tst_QGestureRecognizer::swipeGesture() is flaky as sometimes the
gesture event is being sent before the widget's position has
been updated.

The gesture starts in the window frame.

Set flag Qt::FramelessWindowFrame to prevent this from
happening.

Fix flakiness on Opensuse 15

Pick-to: 6.8
Change-Id: I794b022b5a51146ddfa7d6029509c6fa43b9aad6
Reviewed-by: Axel Spoerl <axel.spoerl@qt.io>
(cherry picked from commit 6dc0e593939cbeaeb45392d8daf7fcd90e8cb0f8)
Reviewed-by: Qt Cherry-pick Bot <cherrypick_bot@qt-project.org>

tests/auto/widgets/kernel/qgesturerecognizer/tst_qgesturerecognizer.cpp

@@ -257,6 +257,7 @@ void tst_QGestureRecognizer::swipeGesture()
     const Qt::GestureType gestureType = Qt::SwipeGesture;
     TestWidget widget(GestureTypeVector(1, gestureType));
     widget.setWindowTitle(QTest::currentTestFunction());
+    widget.setWindowFlag(Qt::FramelessWindowHint);
     widget.show();
     QVERIFY(QTest::qWaitForWindowExposed(&widget));