Incorrect types in IgdDevice.async_(add/delete)_port_mapping

[JurgenR]

In IgdDevice.async_add_port_mapping and IgdDevice.async_delete_port_mapping the types for remote_host and lease_duration do not allow for a None value despite handling them:

• remote_host is modified to an empty string if the value is None
• lease_duration is modified to value 0 if the value is None

https://github.com/StevenLooman/async_upnp_client/blob/e05dae4d293b28da6e3bff759046c9c316321d7e/async_upnp_client/profiles/igd.py#L383

[StevenLooman]

Thank you for this issue @JurgenR. You are right, the handling of None values can be removed, as this will never happen. I'll remove these.

[StevenLooman]

Thanks! This will be included in the next release.