Update changelog for v2.1.9

Author: github-actions[bot]

CHANGELOG.md

@@ -1,6 +1,6 @@
 # CodeQL Action Changelog
 
-## [UNRELEASED]
+## 2.1.9 - 27 Apr 2022
 
 - Add `working-directory` input to the `autobuild` action. [#1024](https://github.com/github/codeql-action/pull/1024)
 - The `analyze` and `upload-sarif` actions will now wait up to 2 minutes for processing to complete after they have uploaded the results so they can report any processing errors that occurred. This behavior can be disabled by setting the `wait-for-processing` action input to `"false"`. [#1007](https://github.com/github/codeql-action/pull/1007)