fix(hydrotherm_dynamic_x8_water_heater): enable changing temperature

On original PR #251, the setting of temperature was disabled "for protection". This was
probably out of excessive caution with the contributor not wanting HA to be the cause of
any overheating or loss of heating situations.

For general case, this should be enabled.

Issue #5820

custom_components/tuya_local/devices/hydrotherm_dynamic_x8_water_heater.yaml

@@ -29,7 +29,6 @@ entities:
         range:
           min: 15
           max: 75
-        readonly: true
       - id: 3
         type: integer
         name: current_temperature