Fix broken RBAC link on welcome page

[github-actions]

Summary

Fixed the broken link detected by the scheduled link checker:

• [404] https://buildwithfern.com/docs/authentication/rbac → Updated href in fern/products/home/pages/welcome.mdx from /docs/authentication/rbac to /docs/authentication/features/rbac

The RBAC page is nested under Authentication > Features in docs.yml (slug: features), so the URL requires the features/ segment. A corresponding redirect already existed in docs.yml for the /learn/docs/authentication/rbac path, confirming the correct destination.

Also deleted the scaffold file .github/broken-links/broken-links.md as instructed.

Review & Testing Checklist for Human

• Verify that the preview deployment link for https://buildwithfern.com/docs/authentication/features/rbac resolves to the RBAC page correctly
• Click the "Control role-based access" button on the welcome/home page and confirm it navigates to the right page

Notes

• Requested by: unknown ()
• Link to Devin run

[github-actions]

🌿 Preview your docs: https://fern-preview-286741bb-2a0c-45b0-8566-1af2a391ec13.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/home

[devin-ai-integration]

Verified the fix using the preview link:

• The RBAC page loads correctly at the preview URL (HTTP 200).
• Also verified locally with fern docs dev — /docs/authentication/features/rbac resolves correctly.

Requesting review from @davidkonigsberg.