Add a note about server ping cleanup

Author: GaneshSPatil

src/main/java/cd/go/contrib/elasticagents/docker/executors/ServerPingRequestExecutor.java

@@ -39,6 +39,7 @@ public ServerPingRequestExecutor(ServerPingRequest serverPingRequest, Map<String
 
     @Override
     public GoPluginApiResponse execute() throws Exception {
+        //todo: remove possiblyMissingAgents, refer to ecs/kubernetes server ping implementation
         Set<Agent> possiblyMissingAgents = new HashSet<>();
         List<ClusterProfileProperties> allClusterProfileProperties = serverPingRequest.allClusterProfileProperties();