docs: add changelog

Author: kenjis

user_guide_src/source/changelogs/v4.2.8.rst

@@ -31,7 +31,7 @@ none.
 Deprecations
 ************
 
-none.
+- The third parameter ``$returnResponse`` of ``CodeIgniter::handleRequest()`` is deprecated, and no longer used.
 
 Bugs Fixed
 **********