geojson test 22 intvalue property is a float

[Kurt Schwehr]

I am pretty sure that the properties don't mean anything, but was there a particular point to having 3.5 for the 'intvalue'?

​https://trac.osgeo.org/gdal/browser/trunk/autotest/ogr/ogr_geojson.py#L928

    if (feature.GetFieldAsString("_id") != 'aid2' or
        feature.GetFieldAsString("_rev") != 'arev2' or
        feature.GetFieldAsDouble("intvalue") != 3.5 or
        feature.GetFieldAsString("str2value") != 'bar' or
        ogrtest.check_feature_geometry(feature, ref_geom) != 0):

If there was a specific reason, we should doc it. If not, I'm considering making it just an int.