docs: fix broken link in AAD docs

[jackfrancis]

Reason for Change:

This PR fixes a broken link in the aad docs.

Issue Fixed:

Credit Where Due:

Does this change contain code from or inspired by another project?

• No
• Yes

If "Yes," did you notify that project's maintainers and provide attribution?

• No
• Yes

Requirements:

• uses conventional commit messages
• includes documentation
• adds unit tests
• tested upgrade from previous version

Notes:

[deaborch]

@jackfrancis would it be possible to include in the documentation that it is not supported in azure stack hub??

[mboersma]

/lgtm

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[jackfrancis]

@deaborch If it indeed true that there is no Azure Stack Hub solution, yeah, we should include that in the docs. Could you submit a PR with the appropriate Azure Stack messaging, if true?