Add check to run only if triggered from MicrosoftDocs repo

[dstrome]

PR Summary

PR Checklist

• Descriptive Title: This PR's title is a synopsis of the changes it proposes.
• Summary: This PR's summary describes the scope and intent of the change.
• Contributor's Guide: I have read the contributors guide.
• Style: This PR adheres to the style guide.

[learn-build-service-prod]

Learn Build status updates of commit 8ebf3f6:

✅ Validation status: passed

File	Status	Preview URL	Details
.github/workflows/AutoLabelAssign.yml	✅Succeeded
.github/workflows/AutoLabelMsftContributor.yml	✅Succeeded
.github/workflows/BackgroundTasks.yml	✅Succeeded
.github/workflows/BuildValidation.yml	✅Succeeded
.github/workflows/LiveMergeCheck.yml	✅Succeeded
.github/workflows/PrFileCount.yml	✅Succeeded
.github/workflows/ProtectedFiles.yml	✅Succeeded
.github/workflows/Stale.yml	✅Succeeded
.github/workflows/StaleBranch.yml	✅Succeeded
.github/workflows/TierManagement.yml	✅Succeeded

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