Add missing routes to make group edits work

6b90ccb9 changed the routes so that users/groups can be accessed via`/:id`, but the Rails `form_for` method expects to use the `groups#show` path helper for the form action URL. This causes group edits and deletes to fail because the PUT/PATCH/DELETE methods did not exist for `/:id`.  This MR adds these methods so that `form_for` continues to work.

Closes #23306 


See merge request !6874