add pending-removal-in-future entry

Author: methane

Doc/deprecations/pending-removal-in-future.rst

@@ -49,6 +49,8 @@ although there is currently no date scheduled for their removal.
   :data:`calendar.FEBRUARY`.
   (Contributed by Prince Roshan in :gh:`103636`.)
 
+* :func:`codecs.open`: use the :func:`open` instead. (:gh:`133038`)
+
 * :attr:`codeobject.co_lnotab`: use the :meth:`codeobject.co_lines` method
   instead.