Merge pull request #4658 from rabbitmq/mergify/bp/v3.9.x/pr-4657

Update 3.9.16 release notes (backport #4656) (backport #4657)

Author: michaelklishin

release-notes/3.9.16.md

@@ -48,6 +48,18 @@ Contributors are encouraged to update them together with their changes. This hel
    GitHub issue: [#4570](https://github.com/rabbitmq/rabbitmq-server/pull/4570)
 
 
+### Prometheus Plugin
+
+#### Bug Fixes
+
+ * One metric that was exposed via CLI tools and management plugin's HTTP API
+   was not exposed via Prometheus scraping API.
+
+   Contributed by @gomoripeti.
+
+   GitHub issue: [#4645](https://github.com/rabbitmq/rabbitmq-server/pull/4645)
+
+
 ## Dependency Upgrades
 
  * `osiris` upgraded from [`1.2.4` to `1.2.6`](https://github.com/rabbitmq/osiris/compare/v1.2.4...v1.2.6)