STL siren: make switch optional

DP 104 does not appear in the log.

custom_components/tuya_local/devices/stl_siren.yaml

@@ -37,6 +37,7 @@ primary_entity:
         max: 60
     - id: 104
       type: boolean
+      optional: true
       name: switch
 secondary_entities:
   - entity: sensor