GitHub introduced a date-based versioning scheme for the API a while ago already: https://github.blog/developer-skills/github/to-infinity-and-beyond-enabling-the-future-of-githubs-rest-api-with-api-versioning/
In this scheme, version v3 is now known as 2022-11-28 (and at time of writing, there haven't been any new versions since).

As far as I can tell, all of the Haddocks still refer to the old location of the API docs at https://developer.github.com/v3, which now redirects to https://docs.github.com/en/rest?apiVersion=2022-11-28. These should be updated to the new URLs, also because sometimes fragments are specified which refer to a heading that now doesn't exist, e.g. in the docs for createCommentR.