Fix broken link to default-values extension page

[github-actions]

Summary

Fixed a broken link in fern/products/sdks/deep-dives/generated-sdk.mdx. The link pointed to /learn/api-definitions/openapi/extensions/default which returns 404. The correct URL is /learn/api-definitions/openapi/extensions/default-values — the page "Default values" in api-def.yml has no explicit slug, so it auto-derives to default-values.

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

Review & Testing Checklist for Human

• Verify the link at /learn/api-definitions/openapi/extensions/default-values resolves correctly in the preview deployment
• Confirm the "Default parameter values" section on the generated SDK page renders the link properly

Notes

The other two files that link to this page (configure-global-headers.mdx and global-headers.mdx) already use the correct /default-values slug.

Link to Devin session: https://app.devin.ai/sessions/d27c27286dc24b1eb662aee7de976613

[github-actions]

🌿 Preview your docs: https://fern-preview-devin-fix-broken-links.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/sdks/deep-dives/sdk-user-features

[devin-ai-integration]

Verified the fix using the preview link:

• The target page /learn/api-definitions/openapi/extensions/default-values returns 200 in the preview.
• The source page /learn/sdks/deep-dives/sdk-user-features renders correctly.
• The original broken URL /learn/api-definitions/openapi/extensions/default still returns 404 on production, confirming this was the correct fix.