Address Centre dissolution; remove instances of 'Centre' throughout.

[jheron-circle]

This PR removes all instances of 'Centre' throughout this repo, and replaces them as appropriate:

• Mostly, with 'Circle' for 'Centre'.
• Updates the licenses with "© 2023 Circle Internet Financial Limited".
• Removes the schema that pointed to a centre.io URL.
• Updates paths in URLs to point to the repo 'github.com/circlefin/verite'.