Update cross-tenant-mailbox-migration.md

[msbemba]

Removed Domain sharing Note as it is not available ATM

Fixes https://github.com/MicrosoftDocs/microsoft-365-docs-pr/issues/23609

[msbemba]

@JohanFreelancer9 Please copy review

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

Learn Build status updates of commit da126e6:

: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.

For any questions, please:

• Try searching the learn.microsoft.com contributor guides
• Post your question in the Learn support channel

[yogkumgit]

@kelleyvice-msft Please merge this PR. Thanks

[yogkumgit]

@kelleyvice-msft Gentle reminder.