Hydrotherm X8: expand set temperature range

Based on the Tuya portal info from #663, the devices can be set from 15 to 75.

The original limit of 60 to 70 may be based on regulatory requirements in a
specific country.

custom_components/tuya_local/devices/hydrotherm_dynamic_x8_water_heater.yaml

@@ -13,8 +13,8 @@ primary_entity:
       type: integer
       name: temperature
       range:
-        min: 60
-        max: 70
+        min: 15
+        max: 75
       readonly: true
     - id: 3
       type: integer