(GH-294) Fix syntax for dsc resource test reference

[michaeltlombardi]

PR Summary

Fixes #294

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.
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• Style: This PR adheres to the style guide.

[learn-build-service-prod]

Learn Build status updates of commit 3fad6a8:

✅ Validation status: passed

File	Status	Preview URL	Details
dsc/docs-conceptual/dsc-3.0/reference/cli/resource/test.md	✅Succeeded	View (dsc-3.0)

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