(GH-359) Fix resource kind

[michaeltlombardi]

PR Summary

Prior to this change, the resource kind in the root manifest reference wasn't updated to reflect the correct casing or all valid options. This change:

• Ensures that the reference in the manifest root matches the subschema reference.
• Fixes "message": "Value is not accepted. Valid values: \"resource\", \"adapter\", \"group\", \"importer\", \"exporter\".", "source": "yaml-schema: Resource kind", #359

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 466b4cf:

✅ Validation status: passed

File	Status	Preview URL	Details
dsc/docs-conceptual/dsc-3.0/reference/schemas/definitions/resourceKind.md	✅Succeeded	View (dsc-3.0)
dsc/docs-conceptual/dsc-3.0/reference/schemas/resource/manifest/root.md	✅Succeeded	View (dsc-3.0)

For more details, please refer to the build report.