Docs: Fix changelog heading

Author: GaryJones

CHANGELOG.md

@@ -18,7 +18,7 @@ The tagged releases branch is now `main` instead of `master`.
 - [#777](https://github.com/Automattic/VIP-Coding-Standards/pull/777): 3.0: start using PHPCSUtils.
 - [#779](https://github.com/Automattic/VIP-Coding-Standards/pull/779): 3.0: support WordPressCS 3.0.
 
-## Changed
+### Changed
 - [#780](https://github.com/Automattic/VIP-Coding-Standards/pull/780): Performance/WPQueryParams: defer to the parent sniff.
   - Two error codes changed:
     - `WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn` is now `WordPressVIPMinimum.Performance.WPQueryParams.PostNotIn_post__not_in`.