Jewish calendar match omer service variables requirement to documentation (#141620)

The documentation and the omer schema require a Nusach to be specified, but the YAML misses that requirement

homeassistant/components/jewish_calendar/services.yaml

@@ -6,6 +6,7 @@ count_omer:
       selector:
         date:
     nusach:
+      required: true
       example: "sfarad"
       default: "sfarad"
       selector: