Remove unused parameters from create-cluster-rac-enabled-disconnected

[prakhar_shukla (shuklaprakhar415)]

PR Checklist

• I have read the Contribution Guide and Best Practices Guide.

Changelog

• Remove the unused securityLevel, networkingType, and networkingPattern declarations from quickstarts/microsoft.azurestackhci/create-cluster-rac-enabled-disconnected/azuredeploy.json.
• Remove their corresponding entries from azuredeploy.parameters.json.
• Leave all resource definitions, parameter references, and remaining parameter values unchanged. These three parameters were not referenced by the template.

Local validation

• Parsed the updated JSON files and confirmed the only structural changes are the intended parameter deletions.
• Confirmed every remaining top-level template parameter is referenced and every sample parameter-file entry is declared by the template.
• git diff --check passed.

Deployment evidence pending

This PR is intentionally a draft. No Azure deployment was performed, and metadata.json was not updated with fabricated or reused deployment evidence. A fresh deployment and its testResult data are required by the contribution guide before this PR is ready; the template/metadata CI gate is expected to remain blocked until then.