ZN373186 temp/humidity: make battery sensor optional

Battery is apparently not reeported consistently with these sensors.

Issue #1636

custom_components/tuya_local/devices/zigbee_zn373186_temphumid_sensor.yaml

@@ -31,5 +31,6 @@ secondary_entities:
       - id: 4
         type: integer
         name: sensor
+        optional: true
         unit: "%"
         class: measurement