[Docs] Revise changelog for version 3.13.2 (#2982)

* Update CHANGELOG entries for 3.13.2 release

Author: hehe7318

CHANGELOG.md

@@ -15,8 +15,9 @@ This file is used to list changes made in each version of the AWS ParallelCluste
 3.13.2
 ------
 
-**CHANGES**
-- Fix build image failures occurring on non-latest versions of Rocky Linux 9.
+**BUG FIXES**
+- Fix `build-image` failure on Rocky 9, occurring when the parent image does not ship the latest kernel version.
+  See https://github.com/aws/aws-parallelcluster/issues/6874.
 
 3.13.1
 ------