[issue47061] Document PEP 594 deprecations

New submission from Brett Cannon : https://peps.python.org/pep-0594/ The SC has asked that all modules deprecated by PEP 594 have the documented deprecation backported. The message should also not have any specific removal version to avoid any potential delay, but then making the bugfix-only

[issue47061] Document PEP 594 deprecations

Change by Brett Cannon : -- dependencies: +PEP 594: Document removal of asynchat, asyncore and smtpd ___ Python tracker ___ ___ Pyth