Update CHANGELOG.md

Author: OsaAjani

CHANGELOG.md

@@ -25,6 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 ### Fixed <!-- for any bug fixes -->
 - Fix ffmpeg reading crash when invalid metadata (see pr #2311)
 - Fix GPU h264_nvenc encoding not working.
+- Improve perfs of decorator by pre-computing arguments
 
 ## [v2.1.2](https://github.com/zulko/moviepy/tree/master)