Add changelog entry for post-processing change

Author: mbg

CHANGELOG.md

@@ -5,6 +5,7 @@ See the [releases page](https://github.com/github/codeql-action/releases) for th
 ## [UNRELEASED]
 
 - Bump minimum CodeQL bundle version to 2.17.6. [#3223](https://github.com/github/codeql-action/pull/3223)
+- When SARIF files are uploaded by the `analyze` or `upload-sarif` actions, the CodeQL Action automatically performs post-processing steps to prepare the data for the upload. Previously, these post-processing steps were only performed before an upload took place. We are now changing this so that the post-processing steps will always be performed, even when the SARIF files are not uploaded. This does not change anything for the `upload-sarif` action. For `analyze`, this may affect Advanced Setup for CodeQL users who specify a value other than `always` for the `upload` input. [#3222](https://github.com/github/codeql-action/pull/3222)
 
 ## 4.30.9 - 17 Oct 2025