ci: replace content-delivery-release-bot with token
ci: replace content-delivery-release-bot with token

For releases to PyPI, migrate away from password-based auth with
content-delivery-release-bot to using a token instead.  (Tokens
were not available at the time content-delivery-release-bot was
introduced.)

Reasons for doing this include:

- the team associated with content-delivery-release-bot doesn't
  exist any more
- tokens are project-scoped, so any accidents which expose this
  token will not put any other projects at risk & won't require
  token resets for any other project

release-engineering/kobo,release-engineering/kobo,release-engineering/kobo,release-engineering/kobo