add docs for health type none

Author: charlesmst

docs/en/actuator.md

@@ -195,6 +195,13 @@ grpc.server.health-service.type=ACTUATOR
 
 The integration allows you to check the health status for the whole service or specific health indicators, where the `service` is the key of the [`HealthIndicator`](https://docs.spring.io/spring-boot/docs/current/reference/html/actuator.html#actuator.endpoints.health.auto-configured-health-indicators).
 `Watch` is not yet supported because actuator is pull-based and does not automatically tries to determine the status of the service to notify clients.
+
+To prevent any health service from being served by the GRPC server, you can set the type to `NONE`:
+
+````properties
+grpc.server.health-service.type=NONE
+````
+
 ## Opt-Out
 
 You can opt out from the actuator autoconfiguration using the following annotation: