update changelog

Author: RobinMalfait

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Handle `'` syntax in ClojureScript when extracting classes ([#18888](https://github.com/tailwindlabs/tailwindcss/pull/18888))
 - Handle `@variant` inside `@custom-variant` ([#18885](https://github.com/tailwindlabs/tailwindcss/pull/18885))
+- Merge suggestions when using `@utility` ([#18900](https://github.com/tailwindlabs/tailwindcss/pull/18900))
 
 ## [4.1.13] - 2025-09-03