Start-MailboxAssistant documentation completed

[lusassl-msft]

FYI @chrisda

[learn-build-service-prod]

Learn Build status updates of commit c90d0b2:

✅ Validation status: passed

File	Status	Preview URL	Details
exchange/exchange-ps/exchange/exchange.md	✅Succeeded	View (exchange-ps)
exchange/exchange-ps/exchange/Start-MailboxAssistant.md	✅Succeeded	View (exchange-ps)
exchange/mapping/serviceMapping.json	✅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

[learn-build-service-prod]

Learn Build status updates of commit 9533306:

✅ Validation status: passed

File	Status	Preview URL	Details
exchange/exchange-ps/exchange/exchange.md	✅Succeeded	View (exchange-ps)
exchange/exchange-ps/exchange/Start-MailboxAssistant.md	✅Succeeded	View (exchange-ps)
exchange/mapping/serviceMapping.json	✅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