Add changelog note for CodeQL v2.10.5 deprecation

CHANGELOG.md

@@ -4,7 +4,9 @@ See the [releases page](https://github.com/github/codeql-action/releases) for th
 
 ## [UNRELEASED]
 
-No user facing changes.
+- Add a deprecation warning for customers using CodeQL version 2.11.5 and earlier. These versions of CodeQL were discontinued on 8 November 2023 alongside GitHub Enterprise Server 3.7, and will be unsupported by the next minor release of the CodeQL Action. [#1993](https://github.com/github/codeql-action/pull/1993)
+  - If you are using one of these versions, please update to CodeQL CLI version 2.11.6 or later. For instance, if you have specified a custom version of the CLI using the 'tools' input to the 'init' Action, you can remove this input to use the default version.
+  - Alternatively, if you want to continue using a version of the CodeQL CLI between 2.10.5 and 2.11.5, you can replace `github/codeql-action/*@v2` by `github/codeql-action/*@v2.22.7` in your code scanning workflow to ensure you continue using this version of the CodeQL Action.
 
 ## 2.22.6 - 14 Nov 2023