Weeket kettle: make operation mode dp optional

Issue #2140, potentially #1985

custom_components/tuya_local/devices/weeket_kettle.yaml

@@ -49,6 +49,7 @@ primary_entity:
           value: C
     - id: 16
       type: string
+      optional: true
       name: operation_mode
       mapping:
         - dps_val: setting_quick