Update MR approvals for SAML

What does this MR do and why?

In MR Add optional SAML Auth requirement for MR approval (!130204 - merged) we are adding the ability to use SAML auth (if it is enabled) to approve MRs. Previously it was only possible to use password auth. This feature is currently on for gitlab.com, instance level SAML will be built next in this issue SAML SSO authentication for merge request appro... (#431415 - closed)

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Before	After

How to set up and validate locally

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MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

doc/user/project/merge_requests/approvals/settings.md

@@ -29,8 +29,8 @@ These settings limit who can approve merge requests:
   Prevents users who add commits to a merge request from also approving it.
 - [**Prevent editing approval rules in merge requests**](#prevent-editing-approval-rules-in-merge-requests):
   Prevents users from overriding project level approval rules on merge requests.
-- [**Require user password to approve**](#require-user-password-to-approve):
-  Force potential approvers to first authenticate with a password.
+- [**Require user re-authentication (password or SAML) to approve**](#require-user-re-authentication-to-approve):
+  Force potential approvers to first authenticate with either a password or with SAML.
 - Code Owner approval removals: Define what happens to existing approvals when
   commits are added to the merge request.
   - **Keep approvals**: Do not remove any approvals.
@@ -104,20 +104,29 @@ on merge requests, you can disable this setting:
 
 This change affects all open merge requests.
 
-## Require user password to approve
+## Require user re-authentication to approve
 
 > - [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/5981) in GitLab 12.0.
 > - Moved to GitLab Premium in 13.9.
+> - SAML authentication for GitLab.com groups [introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/5981) in GitLab 16.6.
 
-You can force potential approvers to first authenticate with a password. This
+You can force potential approvers to first authenticate with either:
+
+- A password.
+- SAML. Available on GitLab.com groups only.
+
+This
 permission enables an electronic signature for approvals, such as the one defined by
 [Code of Federal Regulations (CFR) Part 11](https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?CFRPart=11&showFR=1&subpartNode=21:1.0.1.1.8.3)):
 
-1. Enable password authentication for the web interface, as described in the
-   [sign-in restrictions documentation](../../../../administration/settings/sign_in_restrictions.md#password-authentication-enabled).
+1. Enable password authentication and SAML authentication (available only on GitLab.com groups). For more information on:
+   - Password authentication, see
+     [sign-in restrictions documentation](../../../../administration/settings/sign_in_restrictions.md#password-authentication-enabled).
+   - SAML authentication for GitLab.com groups, see
+     [SAML SSO for GitLab.com groups documentation](../../../../user/group/saml_sso).
 1. On the left sidebar, select **Settings > Merge requests**.
 1. In the **Merge request approvals** section, scroll to **Approval settings** and
-   select **Require user password to approve**.
+   select **Require user re-authentication (password or SAML) to approve**.
 1. Select **Save changes**.
 
 ## Remove all approvals when commits are added to the source branch