[Docs] Discrepency in the intro

[bkotch]

https://zendframework.github.io/zend-permissions-rbac/intro/ mentions

To create a role, extend the abstract class Zend\Permission\Rbac\AbstractRole or use the default role class, Zend\Permission\Rbac\Role. You can instantiate a role and add it to the RBAC container or add a role directly using the RBAC container addRole() method.

But AbstractRole no longer exists in the package. And the migration guide suggests a different way of doing things.

[weierophinney]

This repository has been closed and moved to laminas/laminas-permissions-rbac; a new issue has been opened at laminas/laminas-permissions-rbac#4.