fix: adding missing spc and itn regions to pdns resolver template

[joselcaguilar]

Overview/Summary

Private DNS Resolver cannot be deployed using the accelerator through the Portal Experience in Spain Central and Italy North regions, this service is already available on those regions.

This PR fixes/adds/changes/removes

1. Fix the deployment for Private DNS Resolver in Spain Central and Italy North regions

Breaking Changes

N/A

Testing Evidence

Only added more regions to allowedValues array, region availability per product is here

Testing URLs

Azure Public

Azure US Gov (Fairfax)

As part of this Pull Request I have

• Checked for duplicate Pull Requests
• Associated it with relevant issues, for tracking and closure.
• Ensured my code/branch is up-to-date with the latest changes in the main branch
• Performed testing and provided evidence.
• Ensured contribution guidance is followed.
• Updated relevant and associated documentation.
• Updated the "What's New?" wiki page (located: /docs/wiki/whats-new.md)

[joselcaguilar]

Hi @Azure/alz-core-team-technical team, just following up this PR, in case u need additional context, happy to help ☺️

Thanks in advance!

[jtracey93]

Thank you for your contribution @joselcaguilar!

Due to CI/CD limitations with fork PRs and secrets access, I've migrated your changes to #2137. All your commits and authorship have been preserved. Please follow the new PR for any updates or requested changes.

The new PR will run all required checks and can be merged once approved.