Reconcile duplicate elasticsearch roles pages

[shainaraskas]

same page is in two places:

https://www.elastic.co/docs/deploy-manage/users-roles/cluster-or-deployment-auth/built-in-roles

https://www.elastic.co/docs/reference/elasticsearch/roles

and the info is drifting. likely will need to keep the reference page and make the deploy-manage one an xref only.

[yetanothertw]

PR to add the TOC crosslink: #2811