fix (morento_mr5866_air_purifier): make the config match the log

Issue #4682

Needed to make dp 11 optional. Also added optional dp 19 (time remaining), which
only seems to be reported when the timer is running.

custom_components/tuya_local/devices/morento_mr5866_air_purifier.yaml

@@ -69,6 +69,7 @@ entities:
     dps:
       - id: 11
         name: button
+        optional: true
         type: boolean
 
   - entity: select
@@ -88,6 +89,17 @@ entities:
           - dps_val: 8h
             value: 8h
 
+  - entity: sensor
+    translation_key: time_remaining
+    class: duration
+    category: diagnostic
+    dps:
+      - id: 19
+        type: integer
+        optional: true
+        name: sensor
+        unit: min
+
   - entity: sensor
     translation_key: air_quality
     class: enum