Add changelog note

Author: github-actions[bot]

CHANGELOG.md

@@ -7,6 +7,7 @@ Note that the only difference between `v2` and `v3` of the CodeQL Action is the
 ## [UNRELEASED]
 
 - On Linux, the maximum possible value for the `--threads` option now respects the CPU count as specified in `cgroup` files to more accurately reflect the number of available cores when running in containers. 
+- Update default CodeQL bundle version to 2.16.1. [#2096](https://github.com/github/codeql-action/pull/2096)
 
 ## 3.23.1 - 17 Jan 2024