Feyree EV charger: make clear energy button optional

This should have been optional from the start, as it wasn't in the
original log either, and that is usually expected for reset type buttons.

Issue #1176

custom_components/tuya_local/devices/feyree_ev_charger.yaml

@@ -85,6 +85,7 @@ secondary_entities:
       - id: 16
         type: boolean
         name: button
+        optional: true
   - entity: number
     name: Set charge current
     category: config