fix(Modal): always fullscreen on mobile

[sandros94]

🔗 Linked issue

Resolves #2463

❓ 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)
• ✨ New feature (a non-breaking change that adds functionality)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

It is counterintuitive having a fullscreen prop, but at the same time always displaying fullscreen on mobile by default.

📝 Checklist

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

[pkg-pr-new]

pnpm add https://pkg.pr.new/@nuxt/ui@2637

commit: e3f003e