Revert saml-auth-flow-for-mr-approval feature

What does this MR do and why?

What:

• Revert "Merge branch 'sf/feature/GL421959-saml-auth-flow-for-mr-approval' commit 9de4dca8
• Revert "Merge branch 'nrosandich-master-patch-a068' commit fbb61f43

This merge request reverts SAML MR approval and accompanied documentation change.

Why:

The feature has a bug when trying to approve through SAML when on a nested group and was reverted on master. (Note: this feature should not effect SM. See comments below)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• This MR is backporting a bug fix, documentation update, or spec fix, previously merged in the default branch.
• The MR that fixed the bug on the default branch has been deployed to GitLab.com (not applicable for documentation or spec changes).
• This MR has a severity label assigned (if applicable).
• This MR has been approved by a maintainer (only one approval is required).
• Ensure the e2e:package-and-test-ee job has either succeeded or been approved by a Software Engineer in Test.
• Set the milestone of the merge request to match the target backport branch version.

Note to the merge request author and maintainer

If you have questions about the patch release process, please:

• Refer to the patch release runbook for engineers and maintainers for guidance.
• Ask questions on the #releases Slack channel (internal only).