Remove tst_QWebEnginePage::scrollToAnchor auto test

The tested QWebEnginePage::scrollToAnchor API can't be added to
QtWebEngine for now. Currently, Chromium Content API doesn't support to
control page scroll. The corresponding feature can be used by URL
fragment identifier (#anchor) or JavaScript API (location.href).

Change-Id: Ie9c87758d458858ba677d309a548cdced525557b
Reviewed-by: Allan Sandfeld Jensen <allan.jensen@qt.io>