Use the url field for the project homepage in PyPI

[thibaudcolas]

Spotted while doing data analysis of Wagtail packages. url is specifically meant for the project "Homepage", so is more appropriate than adding a project_urls set to "Home".

[codecov-commenter]

Codecov Report

Patch and project coverage have no change.

Comparison is base (c928f64) 93.09% compared to head (1d5d2c2) 93.09%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #685 +/- ## ======================================= Coverage 93.09% 93.09% ======================================= Files 47 47 Lines 3912 3912 Branches 581 581 ======================================= Hits 3642 3642 Misses 159 159 Partials 111 111 ``` Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wagtail). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=wagtail)

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[zerolab]

@thibaudcolas I discovered the hard way, that this is not the way when using pyproject.toml

see https://packaging.python.org/en/latest/specifications/declaring-project-metadata/#urls now reverted

[thibaudcolas]

🤦 sorry! I wouldn’t even have considered that the possible metadata was different between different build tools