Moebot S: make auto_mode optional

This matches the Parkside mower as previously reported by @TadFocus (issue
deleted at user's request as it contained private info).

Discussion #758 (@tkrynicki)

custom_components/tuya_local/devices/moebot_s_mower.yaml

@@ -1,7 +1,9 @@
-name: MoeBot S series
+name: Lawnmower
 products:
   - id: mvt4l2evgq2l3nkn
     name: MoeBot S20
+  - id: icw5sal7xfcevsve
+    name: Parkside PMRDA 20-Li A1
 primary_entity:
   entity: vacuum
   icon: "mdi:robot-mower"
@@ -77,6 +79,7 @@ primary_entity:
     - id: 114
       type: string
       name: auto_mode
+      optional: true
 secondary_entities:
   - entity: binary_sensor
     name: Error