Handle forbidden error in email template fetching

[ramya18101]

🔧 Changes

• The Terraform email template fetcher now handles 403 Forbidden responses for gated templates (such as async_approval) gracefully.
• Instead of failing or skipping the entire email template export, the CLI skips only the restricted template and continues processing the remaining templates.
• Improves resilience and consistency of auth0 tf generate when tenants include templates that require paid add-ons.

📚 References

• Customer-reported issue with missing email templates during tenant export (ESD-55111)

🔬 Testing

📝 Checklist

• All new/changed/fixed functionality is covered by tests (or N/A)
• I have added documentation for all new/changed functionality (or N/A)