PEP 484: Mark as Final

[hugovk]

BDFL-Delegate Mark Shannon accepted it in May 2015:

• https://mail.python.org/pipermail/python-dev/2015-May/140104.html

[gvanrossum]

I'm sorry, but I would like to preserve the ability to occasionally update PEP 484 if we've found that a particular feature was a bad idea, and there's consensus to stop promoting it. PEP 484 represents the consensus between the maintainers of various static type checkers (e.g. mypy, pytype, Pyre, PyCharm) so it's important to be able to update it.

Examples of significant updates in the last two years: #1072 changed the specification for #type: ignore; #858 added @type_check_only, #821 removed typing.io and typing.re, and (perhaps most importantly) #689 reverted the (mis-)feature that a default of None automatically made a parameter have an Optional type.

[hugovk]

Makes sense, thanks!