Update changelog for v4.31.7

Author: github-actions[bot]

CHANGELOG.md

@@ -2,7 +2,7 @@
 
 See the [releases page](https://github.com/github/codeql-action/releases) for the relevant changes to the CodeQL CLI and language packs.
 
-## [UNRELEASED]
+## 4.31.7 - 05 Dec 2025
 
 - Update default CodeQL bundle version to 2.23.7. [#3343](https://github.com/github/codeql-action/pull/3343)