refactor(netlify): disable `autoSubfolderIndex` for prerendered pages

[alan-agius4]

🔗 Linked issue

❓ Type of change

• [ ] 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• [x] 🐞 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)
• [ ] 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• [ ] ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

This prevents an unnecessary redirect from /page/ to /page when accessing prerendered content.

📝 Checklist

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

[serhalp]

Adding some links for posterity (I referenced these for my own understanding here!):

• prerender.autoSubfolderIndex nitro option: https://nitro.build/config#prerender
• why this avoids a 301 redirect in some cases: https://answers.netlify.com/t/support-guide-how-can-i-alter-trailing-slash-behaviour-in-my-urls-will-enabling-pretty-urls-help/31191#p-86000-im-ssg-lessmy-ssg-uses-static-routing-4

[pi0]

Thanks for sharing context @serhalp I am totally fine with later backporting this also to v2, perhaps via compat date if you confirm this is certainly a better default and low chance of breaking behavior 👍🏼

[pi0]

/cc @danielroe @TheAlexLichter might have some opinions as it affects current Nuxt users if we backport via compat date.