add PIM for Groups to AAD baseline instructions for 7.6 through 7.9

[tkol2022]

🗣 Description

Modify the AAD baseline document instructions for policies 7.6 through 7.9 to incorporate PIM for Groups. There is a coding issue that is currently in the works that aligns with these changes as well.

Closes #920

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[gdasher]

Based on offline discussion, I'm fine with these changes.

[mitchelbaker-cisa]

Went into admin console and checked the updated steps.

[tkol2022]

@nanda-katikaneni ready for merge