Update changelog

CHANGELOG.md

@@ -45,6 +45,7 @@
 - Update AccountImport ([5a2d7e3e](https://github.com/pixelfed/pixelfed/commit/5a2d7e3e))
 - Update ImportPostController, fix IG bug with missing spaces between hashtags ([9c24157a](https://github.com/pixelfed/pixelfed/commit/9c24157a))
 - Update ApiV1Controller, fix mutes in home feed ([ddc21714](https://github.com/pixelfed/pixelfed/commit/ddc21714))
+- Update AP helpers, improve preferredUsername validation ([21218c79](https://github.com/pixelfed/pixelfed/commit/21218c79))
 -  ([](https://github.com/pixelfed/pixelfed/commit/))
 
 ## [v0.11.9 (2023-08-21)](https://github.com/pixelfed/pixelfed/compare/v0.11.8...v0.11.9)