Expand link check to catch self-referential link
Background
gitlab!126997 (merged) corrected a self-referential link i.e. it removed a link to Saml SSO for GitLab.com groups - Configure GitLab from that same section.
This happened due to content being consolidated - content from the previous Role section that had this link was moved to the Configure GitLab section.
Issue
The current link checker at https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/lib/checks/anchors.rb checks for broken links but not self-referential links to the same section that the link is in.
Proposal
Expand the link checker at https://gitlab.com/gitlab-org/gitlab-docs/-/blob/main/lib/checks/anchors.rb to check for self-referential links as well as broken links.