Clarify default 365-day expiration in ARM API example

[Rahiel Akhtar (raheel1906)]

The ARM API example under "Assign a role using Azure Resource Manager API" shows a request body with "duration": "P365D" but does not explain what this default means or how to change it. Readers who copy the example verbatim end up with role assignments that expire after 365 days without a signal that this is configurable.

This change adds a NOTE block immediately after the request body code fence, explaining that the duration field sets a bounded 365-day eligibility and that permanent eligibility requires the role management policy at the target scope to allow it.

Also bumps ms.date to reflect the update.

[prmerger-automator]

Rahiel Akhtar (@raheel1906) : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change. Ken Withee (@kenwith)

[prmerger-automator]

Rahiel Akhtar (@raheel1906) : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change. Ken Withee (@kenwith)

[learn-build-service-prod]

Learn Build status updates of commit 7588047:

✅ Validation status: passed

File	Status	Preview URL	Details
docs/id-governance/privileged-identity-management/pim-resource-roles-assign-roles.md	✅Succeeded

For more details, please refer to the build report.

[Rahiel Akhtar (raheel1906)]

#sign-off

[prmerger-automator]

Invalid command: '#sign-off'. Only the assigned author of one or more file in this PR can sign off. Ken Withee (@kenwith)

[Regan Downer (v-regandowner)]

Marsh Macy (@mmacy-msft)

Can you review the proposed changes?

IMPORTANT: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
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