Add changelog note

Author: henrymercer

CHANGELOG.md

@@ -7,6 +7,7 @@ Note that the only difference between `v2` and `v3` of the CodeQL Action is the
 ## [UNRELEASED]
 
 - Automatically overwrite an existing database if found on the filesystem. [#2229](https://github.com/github/codeql-action/pull/2229)
+- Bump the minimum CodeQL bundle version to 2.12.6. [#2232](https://github.com/github/codeql-action/pull/2232)
 
 ## 3.24.10 - 05 Apr 2024