chore: Update changelog for session refactor

CHANGELOG.md

@@ -5,7 +5,10 @@ Canonical reference for changes, improvements, and bugfixes for Boundary.
 ## Next
 
 ### Bug Fixes
-
+* sessions: Sessions and session connections have been refactored 
+to better isolate transactions and prevent resource contention that caused deadlocks.
+([Issue](https://github.com/hashicorp/boundary/issues/1812),
+  [PR](https://github.com/hashicorp/boundary/pull/1919))
 * scheduler: Fix bug that causes erroneous logs when racing controllers
   attempted to run jobs
   ([Issue](https://github.com/hashicorp/boundary/issues/1903),