Remove explicit Python version requirements from Markdown docs

[hugovk]

Summary

Update httpcore2 docs to say 3.10 is the minimum required.

Or better yet, because these tend to be forgotten each year, let's delete them (and the httpx2 ones) and rely on the package metadata instead?

Checklist

• I understand that this PR may be closed in case there was no previous discussion. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.

[codspeed-hq]

Merging this PR will not alter performance

✅ 7 untouched benchmarks

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_{Comparing hugovk:rm-3.8 (aec396e) with main (8d5f182)}

[Kludex]

Happy to delete them. Wanna update here? 👀

Are you at PyCon US?

[hugovk]

Happy to delete them. Wanna update here? 👀

Updated!

Are you at PyCon US?

No, but will be at PyCon Italia and EuroPython!

[Kludex]

Happy to delete them. Wanna update here? 👀

Updated!

Are you at PyCon US?

No, but will be at PyCon Italia and EuroPython!

See you in 10 days then! 🙏