Default OSM XYZ tile provider URL should use HTTPS and not a hardcoded subsubdomain

[kannes]

A Pull Request felt like overkill. Trivial and quick change:

In https://github.com/qgis/QGIS/blob/master/resources/qgis_global_settings.ini please change the
connections-xyz\OpenStreetMap\url=http://a.tile.openstreetmap.org/{z}/{x}/{y}.png
to
connections-xyz\OpenStreetMap\url=https://tile.openstreetmap.org/{z}/{x}/{y}.png

This is a) HTTPS and b) not hardcoding a specific tile server but allowing OSM's round-robin stuff to be used.

[m-kuhn]

Pull request opened

[kannes]

Thanks!