Yinmik water quality: make pH sensor optional

Improve compatibility.
Discussion #1754

custom_components/tuya_local/devices/yinmik_waterquality_tester.yaml

@@ -32,6 +32,7 @@ secondary_entities:
         type: integer
         name: sensor
         class: measurement
+        optional: true
         mapping:
           - scale: 100
           - dps_val: 1500