PEP 683: Mark Final

[ncoghlan]

• Final implementation has been merged (including tests and docs)
• PEP matches the final implementation
• Any substantial changes since the accepted version approved by the SC/PEP delegate
• Pull request title in appropriate format (PEP 123: Mark Final)
• Status changed to Final (and Python-Version is correct)
• Canonical docs/spec linked with a canonical-doc directive
  (or canonical-pypa-spec for packaging PEPs,
  or canonical-typing-spec for typing PEPs)

Helps #3817

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📚 Documentation preview 📚: https://pep-previews--3824.org.readthedocs.build/

[ericsnowcurrently]

I don't see any issues with the implementation and there we're any major changes after acceptance.

[loic-simon]

Three "TODO" notes remain in the document:

• at the end of the Implementation Summary section

TODO: Update the performance impact for the latest branch (both for GCC and for clang).

• at the end of the Affected API section

TODO: clarify the status of _Py_RefTotal.

• at the end of the Solutions for Accidental De-Immortalization section

TODO: Add a note indicating that the implemented solution does not affect the overall ~performance-neutral~ outcome.

Should they be cleaned / completed now that the pep is marked Final? Or is it not worth bothering?