docs: fix design-kit image path

[right1121]

🔗 Linked issue

None

❓ Type of change

• 📖 Documentation (updates to the documentation or readme)
• 🐞 Bug fix (a non-breaking change that fixes an issue)
• 👌 Enhancement (improving an existing functionality like performance)
• ✨ New feature (a non-breaking change that adds functionality)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

Fixed an incorrect image path in the design-kit documentation.
This change ensures the image displays properly in the rendered content.

📝 Checklist

• I have linked an issue or discussion.
• I have updated the documentation accordingly.

[pkg-pr-new]

npm i https://pkg.pr.new/@nuxt/content@3366

commit: e69fcb1

[farnabaz]

Thanks