3.10.5 release notes update

(cherry picked from commit aef3741)

Author: michaelklishin

release-notes/3.10.5.md

@@ -13,6 +13,15 @@ Erlang version requirements for RabbitMQ.
 Release notes can be found on GitHub at [rabbitmq-server/release-notes](https://github.com/rabbitmq/rabbitmq-server/tree/v3.10.x/release-notes).
 
 
+### Core Server
+
+#### Bug Fixes
+
+ * Quorum queue could run into an exception when dead lettering a message
+   under certain conditions.
+
+   GitHub issue: [#4947](https://github.com/rabbitmq/rabbitmq-server/pull/4947)
+
 ### Debian Package
 
  * RabbitMQ Debian package now lists Erlang 25.0 as supported.