As discussed with dobedobedoh it would be good to prevent users from being able to create new pages in the old docs https://docs.moodle.org/dev - but retain their ability to edit existing pages. This is because some pages still need improving before migrating to the new developer docs but any new pages should be made on the new docs.
It seems new users in the dev docs are autoconfirmed users so their abiliy to creat new pages should be removed, ie, createpage
See https://docs.moodle.org/dev/Special:ListGroupRights
Hopefully one of our community developers with server access can do this? https://www.mediawiki.org/wiki/Manual:User_rights
(thanks tsala for the advice)

Additionally... we should have a site notice making this clear to users.