Update 3.10.0 release notes

Author: michaelklishin

release-notes/3.10.0.md

@@ -219,6 +219,12 @@ This release includes all bug fixes that shipped in `3.9.x` releases.
 
    GitHub issue: [#4276](https://github.com/rabbitmq/rabbitmq-server/issues/4276)
 
+ * `rabbitmqadmin` now correctly loads TLS-related keys from its configuration file.
+
+   Contributed by @fwolfsjaeger.
+
+   GitHub issue: [#4408](https://github.com/rabbitmq/rabbitmq-server/pull/4408)
+
 
 ### OAuth 2 AuthN and AuthZ Backend Plugin