Update CHANGELOG.md

Author: MartinJJones

CHANGELOG.md

@@ -11,6 +11,7 @@
 
 * Remove unneeded Sass mixins ([PR #4969](https://github.com/alphagov/govuk_publishing_components/pull/4969))
 * Upgrade to LUX version 4.3.2 ([PR #5018](https://github.com/alphagov/govuk_publishing_components/pull/5018))
+* Restructure HTML and use flexbox in super navigation component ([PR #4997](https://github.com/alphagov/govuk_publishing_components/pull/4997))
 
 ## 60.2.1