Update CHANGELOG.md

Author: aeisenberg

CHANGELOG.md

@@ -6,7 +6,7 @@ Note that the only difference between `v2` and `v3` of the CodeQL Action is the
 
 ## [UNRELEASED]
 
-- _Deprecation:_ Swift analysis on Ubuntu runner images is no longer supported. Please migrate to a macOS runner if this affects you.
+- _Deprecation:_ Swift analysis on Ubuntu runner images is no longer supported. Please migrate to a macOS runner if this affects you. [#2403](https://github.com/github/codeql-action/pull/2403)
 
 ## 3.25.15 - 26 Jul 2024