Force update ZHA electrical sensor (#14649)

* force state update because we have a real reading

* hound

* docstring

homeassistant/components/sensor/zha.py

@@ -198,6 +198,11 @@ class ElectricalMeasurementSensor(Sensor):
         """Return the unit of measurement of this entity."""
         return 'W'
 
+    @property
+    def force_update(self) -> bool:
+        """Force update this entity."""
+        return True
+
     @property
     def state(self):
         """Return the state of the entity."""