Update AAD baseline to include PIM for Groups (the return of)

[tkol2022]

Updates the AAD baseline document section 7 privileged user policy instructions to include steps for organizations that are using PIM for Groups. For a description of the changes made refer to #376 (comment).

Closes #376
Closes #797

✅ Pre-approval checklist

• This PR has an informative and human-readable title.
• Changes are limited to a single goal - eschew scope creep!
• All future TODOs are captured in issues, which are referenced
  in code comments.
• All relevant type-of-change labels have been added.
• I have read the CONTRIBUTING document.
• These code changes follow cisagov code standards.
• All relevant repo and/or project documentation has been updated
  to reflect the changes in this PR.
• Tests have been added and/or modified to cover the changes in this PR.
• All new and existing tests pass.

✅ Pre-merge checklist

• Revert dependencies to default branches.
• Finalize version.

✅ Post-merge checklist

• Create a release.

[ssatyapal123]

Looks good