Fix links in PyPI Simple Repository API page (#30594) (#30612)

Fix links in PyPI Simple Repository API page (#30594) (#30612)

Backport #30594 by wxiaoguang

Thanks to @Zottelchen for looking into problem and proposing the fix.

Ref: https://github.com/astral-sh/uv/issues/3017 ,
https://peps.python.org/pep-0503/

This PR's change is from Zottelchen's work.

And I by the way rename the `$p` to `$pd` because `p` is used as
"package" in code, while `pd` is used as "package description".

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Co-authored-by: Zottelchen
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>