Add entry to CHANGES.rst as requested in the PR template

Author: echoix

CHANGES.rst

@@ -43,6 +43,10 @@ Features added
   Patch by Adam Turner.
 * #13647: LaTeX: allow more cases of table nesting.
   Patch by Jean-François B.
+* #13668: :mod:`sphinx.ext.apidoc`: Support :confval:`apidoc_remove_old` 
+  and :code-py:`'remove_old'` key of :confval:`apidoc_modules` when using apidoc as
+  an extension, like :option:`sphinx-apidoc --remove-old`.
+  Patch by Edouard Choinière.
 
 Bugs fixed
 ----------