Add descriptions to granular federation control field

[krammerliu]

Add descriptions to granular federation control field

[learn-build-service-prod]

Learn Build status updates of commit 8f0e276:

✅ Validation status: passed

File	Status	Preview URL	Details
teams/teams-ps/teams/Set-CsExternalAccessPolicy.md	✅Succeeded	View (teams-ps)
teams/teams-ps/teams/Set-CsTenantFederationConfiguration.md	✅Succeeded	View (teams-ps)

For more details, please refer to the build report.

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• Try searching the learn.microsoft.com contributor guides
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[michbrown-png]

@krammerliu - can you please remove all the instances where "Skype for Business Online" is mentioned? It is now deprecated

[learn-build-service-prod]

Learn Build status updates of commit 96a32ee:

✅ Validation status: passed

File	Status	Preview URL	Details
teams/teams-ps/teams/Set-CsExternalAccessPolicy.md	✅Succeeded	View (teams-ps)
teams/teams-ps/teams/Set-CsTenantFederationConfiguration.md	✅Succeeded	View (teams-ps)

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 b35fdb0:

✅ Validation status: passed

File	Status	Preview URL	Details
teams/teams-ps/teams/Set-CsExternalAccessPolicy.md	✅Succeeded	View (teams-ps)
teams/teams-ps/teams/Set-CsTenantFederationConfiguration.md	✅Succeeded	View (teams-ps)

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