fix (m515_curtain_motor): do not map dp 7 to action

The range of values only includes opening and closing, it is missing
opened and closed states, which would still be OK if the value was only sent
by the device when actively opening or closing, but unfortunately it seems
to remain on one of the two states, making it a false description of the
actual state of the device.

Discussion #3730

custom_components/tuya_local/devices/m515_curtain_motor.yaml

@@ -23,9 +23,8 @@ entities:
           min: 0
           max: 100
       - id: 7
-        name: action
+        name: work_state
         type: string
-        persist: false
         optional: true
         mapping:
           - dps_val: opening