deps: click range & advertised Python version

[GabDug]

Hey @awalin,

Just a small update to:

• align the docs with the Python version declared in pyproject.toml (& required by dependencies like pymdown-extensions)
• remove the click upper-range, which is not required anymore and is generating renovate churn with bumps
  • In fix: reload broken with latest click #321 I set an upper-range as we didn't know when the dependency was going to be fixed, we now know that only 8.3.* breaks the auto-reload.
  • the current range could (theoretically) allow a broken click version to be installed, which is counter-productive

Thanks again for all your work!

[awanlin]

Thanks, always keeping this clean @GabDug, much appreciated! 🙏