docs(package-discovery): prioritise pyproject.toml

[mkniewallner]

Summary of changes

"Package Discovery" page is the only one where pyproject.toml examples appear last, so this updates the examples to have them first instead.

Second commit is unrelated, but I found some inconsistencies and thought it could be an opportunity to fix them.

As this is a minor change, I'm not sure if a news entry should be added.

Pull Request Checklist

• Changes have tests
• News fragment added in newsfragments/.
  (See documentation for details)