gh-38877: Update Pypi.io domain (301 permanent redirect)
Which itself redirect pypi.io/(*) to pypi.org/$1,
anything under /package/ redirect directly to files.pythonhosted.org.
Pypi.io is legacy/was temporary so it's a nice things to maybe one day
let the pypa infra team to stop supporting it.
; the pypi.org -> files.pythonhosted.org just avoids an extra redirect,
(Note that one of the changed files is a Python file).
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preview.
### :hourglass: Dependencies
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URL: https://github.com/sagemath/sage/pull/38877
Reported by: M Bussonnier
Reviewer(s): Kwankyu Lee
