Arlec 12-speed fan: use nature for natural dp

Issue #542

custom_components/tuya_local/devices/arlec_12speed_tower_fan.yaml

@@ -13,7 +13,7 @@ primary_entity:
       mapping:
         - dps_val: normal
           value: Normal
-        - dps_val: natural
+        - dps_val: nature
           value: Natural
         - dps_val: sleep
           value: Sleep