fix(cleanair_ca702_dehumidifier): mark DP19 (water-tank fault) as optional (#5086)

DP19 is only emitted by the CA-702 firmware on a real fault event (water
tank full). On a clean device the discovery DPS poll omits DP19, so the
strict-DPS matcher rejects the profile at config-flow and the device
falls back to a generic profile (observed: matched to desk_lamp at 44%).

Marking DP19 as optional on both DP entries inside the class:problem
binary_sensor block matches the upstream convention already used for
the same fault-DP shape on eeese_anna_dehumidifier (DP19), arida_s7l2
and breville_lad208 (DP11). The CA-702 has a unique product_id
(bgo09goklrcdwqg7) so the regression surface is limited to its own
DPS-fallback path.

custom_components/tuya_local/devices/cleanair_ca702_dehumidifier.yaml

@@ -58,12 +58,14 @@ entities:
       - id: 19
         type: bitfield
         name: sensor
+        optional: true
         mapping:
           - dps_val: 0
             value: false
           - value: true
       - id: 19
         type: bitfield
+        optional: true
         name: fault_code
   - entity: sensor
     class: temperature