Adapt to the libgweather API changes
The deprecated GweatherForecastType enumeration was dropped from the API, and gweather_info_new() lost the forecast type parameter.
This requires bumping up the minimum version of libgweather we require to build Calendar. Ideally, we could do a version check and an ifdef dance to keep Calendar building with the previous versions of libgweather, but since we were requiring version 3.24 I don't think it's worth it.