Update Get-AuthenticationPolicy

[samantharamon]

Reverts previous updates to the description of the AllowLegacyExchangeTokens switch.

[learn-build-service-prod]

Learn Build status updates of commit 94286f3:

✅ Validation status: passed

File	Status	Preview URL	Details
exchange/exchange-ps/exchange/Get-AuthenticationPolicy.md	✅Succeeded	View (exchange-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 7c7df7d:

✅ Validation status: passed

File	Status	Preview URL	Details
exchange/exchange-ps/exchange/Get-AuthenticationPolicy.md	✅Succeeded	View (exchange-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