Updated CHANGELOG.md in preparation for v2.3.1 release

CHANGELOG.md

@@ -5,15 +5,15 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
 ## [2.3.1] - 2020-08-20
-### Fixed
-- Fixed bug from v2.3: If default slugifier is used (UniqueSlugify.php), then ensure unique instance each time `MarkupFixer::fix()` is run
-  This will prevent it from continuing to generate unique slugs if used more than once.
-
 ### Changed
 - Minor comment fixes and make arguments optional in service constructors
 - (dev) Added `*.cache` to gitignore (mostly for PHPUnit)
 - (dev) Made compatible with PHPUnit v9 and updated `phpunit.xml.dist` schema
 
+### Fixed
+- Fixed bug from v2.3: If default slugifier is used (UniqueSlugify.php), then ensure unique instance each time `MarkupFixer::fix()` is run
+  This will prevent it from continuing to generate unique slugs if used more than once.
+
 ## [2.3] - 2020-07-16
 ### Added
 - Ability to inject the slugify class (#26) (thanks @yaquawa)