One more 4.1.0 release notes update

Author: michaelklishin

release-notes/4.1.0.md

@@ -32,6 +32,17 @@ For example, certain required feature flags will now be enabled on node boot whe
 See core server changes below as well as the [GitHub project dedicated to feature flags improvements](https://github.com/orgs/rabbitmq/projects/4/views/1)
 for the complete list of related changes.
 
+### rabbitmqadmin v2
+
+[`rabbitmqadmin` v2](https://github.com/rabbitmq/rabbitmqadmin-ng) is a major revision of the
+original CLI client for the RabbitMQ HTTP API.
+
+It supports a much broader set of operations, including health checks, operations
+on federation upstreams, shovels, transformations of exported definitions,
+(some) Tanzu RabbitMQ HTTP API endpoints, `--long-option` and subcommand inference in interactive mode,
+and more.
+
+
 
 ## Breaking Changes and Compatibility Notes