Fix deprecated token field in release script

[anoadragon453]

This field became deprecated in PyGitHub 1.59.0: PyGithub/PyGithub@fc2d0e1

Drop the deprecated field and bump the minimum version we support to 1.59.0.

Most distros are on 2.x of this library already: https://pkgs.org/search/?q=pygithub&on=name

Pull Request Checklist

• Pull request is based on the develop branch
• Pull request includes a changelog file. The entry should:
  • Be a short description of your change which makes sense to users. "Fixed a bug that prevented receiving messages from other servers." instead of "Moved X method from EventStore to EventWorkerStore.".
  • Use markdown where necessary, mostly for code blocks.
  • End with either a period (.) or an exclamation mark (!).
  • Start with a capital letter.
  • Feel free to credit yourself, by adding a sentence "Contributed by @github_username." or "Contributed by [Your Name]." to the end of the entry.
• Code style is correct (run the linters)