GeoRSS: remove OGRGeoRSS_GetGMLEnvelope() that is now useless (#4941)

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25445 f0d54148-0727-0410-94bb-9a71ac55c965
Should have gone with previous commit

git-svn-id: https://svn.osgeo.org/gdal/trunk/gdal@25446 f0d54148-0727-0410-94bb-9a71ac55c965