Update ruff_python_parser README for crates.io

[dhruvmanila]

Summary

This PR updates the parser README to:

1. Link the parser README's AST reference to the published ruff_python_ast crate
2. Remove the obsolete "Python version support" section now that version specific syntax errors are implemented

Additionally, I've also updated the README generator to add a "Versioning" section while preserving the rest of the handwritten README and updated the generator to refresh marker-delimited versioning sections. Maybe this is not worth doing, let me know if that's the case.

Review

• 5a4145a - updates the README manually as mentioned in (1) and (2) above
• dcb5925 - updates the README generator to add the versioning section

Test plan

Here's the Rendered README for preview.

Ran uv run --script scripts/generate-crate-readmes.py twice and verified idempotent output

[dhruvmanila]

The formatter also has a custom README, if we decide to go forward with adding the versioning section for the parser, I can follow-up with adding this section to the formatter and other manually written READMEs as well.

[astral-sh-bot]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[MichaReiser]

Just so that I understand the change. The EGIN GENERATED CRATE VERSIONING support in generate-crate-readmes is needed for crates that contain other content than just the versioning blurb.

[dhruvmanila]

Yes. If the README already exists with some content, the script didn't do anything. But now it will add the blurb if this "BEGIN ...", "END ..." comment pair exist.

[MichaReiser]

Thank you