Fix unit_of_measurement for windspeed to mph in rtl_433_mqtt_hass.py (#3337)

Author: brandon099

examples/rtl_433_mqtt_hass.py

@@ -350,7 +350,7 @@
         "config": {
             "device_class": "wind_speed",
             "name": "Wind Speed",
-            "unit_of_measurement": "mi/h",
+            "unit_of_measurement": "mph",
             "value_template": "{{ value|float }}",
             "state_class": "measurement"
         }