transmission: fix dead link in description (#507032)

          `.config/transmission-daemon/settings.json`

          (each time the service starts).

          See [Transmission's Wiki](https://github.com/transmission/transmission/wiki/Editing-Configuration-Files)

          See [Transmission's documentation](https://github.com/transmission/transmission/blob/main/docs/Editing-Configuration-Files.md#options)

          for documentation of settings not explicitly covered by this module.

        '';

        default = { };