Contractor: Maintainer or Owner (not "at least")

GitLab has a list of roles, lowest to highest:

We used to say "You must have at least the Developer role."

We now want to be more specific. For example: "You must have the Developer, Owner, or Maintainer role."

When the Maintainer role is the minimum required role:

• Use: the Maintainer or Owner role
• Instead of: at least the Maintainer role

The word list has all of these terms and the proper usage. https://docs.gitlab.com/development/documentation/styleguide/word_list/

This issue is to start bulk updating some of this language, which is used primarily in Prerequisites.

Related to: !214564 (merged)