Fix shelly dimmer current sensor device class (#4385)

fixes https://github.com/esphome/issues/issues/4086

esphome/components/shelly_dimmer/light.py

@@ -22,6 +22,7 @@ from esphome.const import (
     UNIT_WATT,
     DEVICE_CLASS_POWER,
     DEVICE_CLASS_VOLTAGE,
+    DEVICE_CLASS_CURRENT,
 )
 from esphome.core import HexInt, CORE
 
@@ -169,7 +170,7 @@ CONFIG_SCHEMA = (
             ),
             cv.Optional(CONF_CURRENT): sensor.sensor_schema(
                 unit_of_measurement=UNIT_AMPERE,
-                device_class=DEVICE_CLASS_POWER,
+                device_class=DEVICE_CLASS_CURRENT,
                 accuracy_decimals=2,
             ),
             # Change the default gamma_correct setting.