update changelog

Author: RobinMalfait

CHANGELOG.md

@@ -10,6 +10,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed
 
 - Fix `@apply` in files without `@tailwind` directives ([#6580](https://github.com/tailwindlabs/tailwindcss/pull/6580))
+- CLI: avoid unnecessary writes to output files ([#6550](https://github.com/tailwindlabs/tailwindcss/pull/6550))
 
 ## [3.0.9] - 2022-01-03