Add changelog note

Author: github-actions[bot]

CHANGELOG.md

@@ -5,6 +5,7 @@ See the [releases page](https://github.com/github/codeql-action/releases) for th
 ## [UNRELEASED]
 
 - Dependency caching should now cache more dependencies for Java `build-mode: none` extractions. This should speed up workflows and avoid inconsistent alerts in some cases.
+- Update default CodeQL bundle version to 2.20.7. [#2810](https://github.com/github/codeql-action/pull/2810)
 
 ## 3.28.11 - 07 Mar 2025