Clarify SAML and LDAP for Authentication to Provision ownership transition

Why is this change being made?

Previously, we moved certain features that Authentication previously owned to the Category:User Management so that they would become owned by groupprovision as part of the relignment.

However, there is still some confusion on ownership when it comes to LDAP and SAML features, since there is joint ownership:

• groupauthentication Owns SAML and LDAP authentication
• groupprovision Owns user lifecycle management with SAML and LDAP, including group sync

This MR aims to make this distinction more clear

Related to Govern::Authentication - Category and Feature U... (Product#13607) and https://gitlab.com/gitlab-org/govern/authentication/discussion/-/issues/134+ and https://gitlab.com/gitlab-com/sec-sub-department/meta/-/issues/1+

CHANGEME

Author and Reviewer Checklist

Please verify the check list and ensure to tick them off before the MR is merged.

• Provided a concise title for this Merge Request (MR)
• Added a description to this MR explaining the reasons for the proposed change, per say why, not just what
  • Copy/paste the Slack conversation to document it for later, or upload screenshots. Verify that no confidential data is added, and the content is SAFE
• Assign reviewers for this MR to the correct Directly Responsible Individual/s (DRI)
  • If the DRI for the page/s being updated isn’t immediately clear, then assign it to one of the people listed in the Maintained by section on the page being edited
  • If your manager does not have merge rights, please ask someone to merge it AFTER it has been approved by your manager in #mr-buddies
  • The when to get approval handbook section explains the workflow in more detail
• For transparency, share this MR with the audience that will be impacted.
  • Team: For changes that affect your direct team, share in your group Slack channel
  • Department: If the update affects your department, share the MR in your department Slack channel
  • Company: If the update affects all (or the majority of) GitLab team members, post an update in #whats-happening-at-gitlab linking to this MR
    • For high-priority company-wide announcements work with the internal communications team to post the update in #company-fyi and align on a plan to circulate in additional channels like the "While You Were Iterating" Newsletter

Commits

• Update file features.yml

---