Update Get-RetentionCompliancePolicy.md

[vilega]

Updating description and explanation for RetentionRuleTypes swicth to avoid customer's confusions if a policy has or not rules and what will be displayed in the output.

[learn-build-service-prod]

Learn Build status updates of commit 10300d2:

✅ Validation status: passed

File	Status	Preview URL	Details
exchange/exchange-ps/exchange/Get-RetentionCompliancePolicy.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
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[learn-build-service-prod]

Learn Build status updates of commit ae38340:

✅ Validation status: passed

File	Status	Preview URL	Details
exchange/exchange-ps/exchange/Get-RetentionCompliancePolicy.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