4.2.0 release notes updates

Author: michaelklishin

release-notes/4.2.0.md

@@ -149,7 +149,11 @@ for release notes of individual releases.
 
 This release series supports upgrades from `4.1.x`, `4.0.x` and `3.13.x`.
 
-[Blue/Green Deployment](https://www.rabbitmq.com/docs/blue-green-upgrade)-style upgrades are avaialble for migrations
+If upgrading from a `3.13.x` cluster that uses classic mirrored queues,
+take a look at what modern CLI tools can offer [for such migrations away from classic mirrored queues](https://www.rabbitmq.com/blog/2025/07/29/latest-benefits-of-rmq-and-migrating-to-qq-along-the-way)
+via [Blue/Green deployments](https://www.rabbitmq.com/docs/blue-green-upgrade).
+
+[Blue/Green Deployment](https://www.rabbitmq.com/docs/blue-green-upgrade)-style upgrades are available for migrations
 from RabbitMQ `3.12.x` series.
 
 ### New Required Feature Flags