fix: error in hass logs

Temperature conversion functions were moved. This fixes the module import.

fixes: #215

custom_components/optimal_humidity/sensor.py

@@ -30,6 +30,8 @@
 
 from homeassistant import util
 
+from homeassistant.util.temperature import fahrenheit_to_celsius
+
 from homeassistant.util.unit_system import METRIC_SYSTEM
 
 from homeassistant.components.sensor import (
@@ -316,7 +318,7 @@ def _update_temp_sensor(state):
             return None
 
         if unit == TEMP_FAHRENHEIT:
-            return util.temperature.fahrenheit_to_celsius(temp)
+            return fahrenheit_to_celsius(temp)
         if unit == TEMP_CELSIUS:
             return temp
         _LOGGER.warning(