Add release notes

Author: ansd

release-notes/4.2.1.md

@@ -0,0 +1,11 @@
+## RabbitMQ 4.2.1
+
+RabbitMQ `4.2.1` is a maintenance release in the `4.2.x` [release series](https://www.rabbitmq.com/release-information).
+
+### Core Server
+
+#### Bug Fixes
+
+ * Quorum queue at-most-once dead lettering for the overflow behaviour `drop-head` now happens in the correct order.
+
+   GitHub issue: [#14926](https://github.com/rabbitmq/rabbitmq-server/pull/14926)

release-notes/4.3.0.md

@@ -57,6 +57,12 @@ compared to other versions.
 
 ### Core Server
 
+#### Bug Fixes
+
+ * Quorum queue at-most-once dead lettering for the overflow behaviour `drop-head` now happens in the correct order.
+
+   GitHub issue: [#14926](https://github.com/rabbitmq/rabbitmq-server/pull/14926)
+
 #### Enhancements
 
 TBD