incorrect link

[MaratMussabekov]

trafficstars

the provided link is for Azure Portal, not for Azure AD Portal

[learn-build-service-prod[bot]]

Learn Build status updates of commit 5a56b0a:

:white_check_mark: Validation status: passed

File	Status	Preview URL	Details
microsoft-365/enterprise/cross-tenant-mailbox-migration.md	:white_check_mark:Succeeded

For more details, please refer to the build report.

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[yogkumgit]

@kelleyvice-msft Please merge this PR. Thanks