Broken extlinks handling for links to Scout repo in documentation

Extlinks (defined at [L405–L413 in conf.py](https://github.com/trynthink/scout/blob/master/docs/conf.py#L405-L413)) are not loading correctly. The effect can be seen on, for example, the [Heating and Cooling Load Components page](https://scout-bto.readthedocs.io/en/latest/thermal_load_components.html).