Fix broken markdown links to turbolinks.md

Updated two broken links in react-router.md that were pointing to the old
location ../rails/turbolinks.md which no longer exists.

The turbolinks.md file was moved from docs/rails/ to docs/building-features/
during the PR #1845 documentation reorganization, but these links were not
updated at that time.

Changes:
- ../rails/turbolinks.md → ./turbolinks.md (same directory)

This fixes the markdown-link-check CI failure:
ERROR: 1 dead link found in docs/building-features/react-router.md !
[✖] ../rails/turbolinks.md → Status: 400

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ihabadham

docs/building-features/react-router.md

@@ -14,7 +14,7 @@ If you're using Turbo (Rails 7+) or Turbolinks (Rails 6 and earlier), be aware t
 
 If you successfully integrate both, please share your solution with the community!
 
-For more details, see [Turbo/Turbolinks Guide](../rails/turbolinks.md).
+For more details, see [Turbo/Turbolinks Guide](./turbolinks.md).
 
 ## Installation
 
@@ -180,4 +180,4 @@ For a practical example of route organization, see the [routes configuration fil
 
 - [React Router Official Documentation](https://reactrouter.com/)
 - [React Router v6 Migration Guide](https://reactrouter.com/en/main/upgrading/v5) - If upgrading from v5
-- [React on Rails Turbo/Turbolinks Guide](../rails/turbolinks.md)
+- [React on Rails Turbo/Turbolinks Guide](./turbolinks.md)