4.2.0 release notes updates

Author: michaelklishin

release-notes/4.2.0.md

@@ -222,6 +222,8 @@ This section is **incomplete** and will be expanded as 4.2 approaches its releas
 ### Dependency Changes
 
  * `ra` was upgraded to [`2.17.1`](https://github.com/rabbitmq/ra/releases)
+ * `khepri` was upgraded to [`0.17.2`](https://github.com/rabbitmq/khepri/releases)
+ * `khepri_mnesia_migration` was upgraded to [`0.8.0`](https://github.com/rabbitmq/khepri_mnesia_migration/releases)
  * `cuttlefish` was upgraded to [`3.5.0`](https://github.com/kyorai/cuttlefish/releases)