Correct NSG rules for DocumentDB connection troubleshooting

[jasonhumsft]

The port is wrong, and the subnet of private endpoint should allow inbound connectivity instead of outbound.

Reference document: https://learn.microsoft.com/en-us/azure/documentdb/troubleshoot-common-issues#debugging-connectivity-issues

[prmerger-automator]

@jasonhumsft : Thanks for your contribution! The author(s) and reviewer(s) have been notified to review your proposed change.

[learn-build-service-prod]

Learn Build status updates of commit 9f8ff49:

✅ Validation status: passed

File	Status	Preview URL	Details
articles/documentdb/how-to-private-link.md	✅Succeeded

For more details, please refer to the build report.

[ShannonLeavitt]

@khelanmodi - Could you review the proposed changes?

IMPORTANT: When the changes are ready for publication, adding a #sign-off comment is the best way to signal that the PR is ready for the review team to merge.

#label:"aq-pr-triaged"
@MicrosoftDocs/public-repo-pr-review-team

[github-actions]

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