[docs] [issue16574] clarify policy on updates to final peps

Roundup Robot added the comment: New changeset 0c4006b7c7ff by Berker Peksag in branch 'default': Issue #16574: Clarify that once a PEP has implemented, it needs be https://hg.python.org/devguide/rev/0c4006b7c7ff ---------- nosy: +python-dev _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue16574> _______________________________________