Change the device class of the smart sensor from humidity to moisture

[DNier]

Fixes https://github.com/py-smart-gardena/hass-gardena-smart-system/issues/213

[grm]

Thx for the PR, I merge it. !

[Bucky2k]

Sorry, this is actually not working on my side just yet. Moisture is not exposed by the integration, the entity is invalid.

@grm info @DNier Any idea what could be wrong? The new entity shows up, but does not contain a valid state. It's not fed by the sensor

I have a mower and one soil sensor

[Bucky2k]

[crazyfx1]

The py-smart-gardena lib does not return "soil_moisture" but still "soil_humidity". Either change it back or adapt the library and push a new version: https://github.com/py-smart-gardena/py-smart-gardena/blob/master/src/gardena/devices/soil_sensor.py