Thermoval TVT40: specify temperature units

This seems to be a requirement of HA now.

custom_components/tuya_local/devices/thermoval_tvt40_thermostat.yaml

@@ -9,6 +9,7 @@ primary_entity:
     - id: 2
       name: temperature
       type: integer
+      unit: C
       range:
         min: 50
         max: 400