fix (smartplug_usb): fix ayailable attribute types

copy/paste error

custom_components/tuya_local/devices/smartplug_usb.yaml

@@ -156,7 +156,7 @@ entities:
           - dps_val: last
             value: memory
       - id: 38
-        type: integer
+        type: string
         optional: true
         name: available
         mapping:
@@ -180,7 +180,7 @@ entities:
           - dps_val: none
             value: "off"
       - id: 39
-        type: integer
+        type: string
         optional: true
         name: available
         mapping: