addAnnotation: added the various entity type supported by the api call (#7478)

This PR adds documentation to the addAnnotation api call

https://cloudstack.apache.org/api/apidocs-4.18/apis/addAnnotation.html

Co-authored-by: Kiran Chavala <kiranchavala@Kirans-MacBook-Air.local>

Author: kiranchavala

api/src/main/java/org/apache/cloudstack/api/command/admin/annotation/AddAnnotationCmd.java

@@ -41,7 +41,7 @@ public class AddAnnotationCmd extends BaseCmd {
     @Parameter(name = ApiConstants.ANNOTATION, type = CommandType.STRING, description = "the annotation text")
     private String annotation;
 
-    @Parameter(name = ApiConstants.ENTITY_TYPE, type = CommandType.STRING, description = "the entity type (only HOST is allowed atm)")
+    @Parameter(name = ApiConstants.ENTITY_TYPE, type = CommandType.STRING, description = "The following entity types are allowed VM, VOLUME, SNAPSHOT, VM_SNAPSHOT, INSTANCE_GROUP, SSH_KEYPAIR, USER_DATA, NETWORK, VPC, PUBLIC_IP_ADDRESS, VPN_CUSTOMER_GATEWAY, TEMPLATE, ISO, KUBERNETES_CLUSTER, SERVICE_OFFERING, DISK_OFFERING, NETWORK_OFFERING, ZONE, POD, CLUSTER, HOST, DOMAIN, PRIMARY_STORAGE, SECONDARY_STORAGE, VR, SYSTEM_VM, AUTOSCALE_VM_GROUP, MANAGEMENT_SERVER")
     private String entityType;
 
     @Parameter(name = ApiConstants.ENTITY_ID, type = CommandType.STRING, description = "the id of the entity to annotate")