docs: remove nuxt 2 information from generate schema

[danielroe]

🔗 Linked issue

nuxt/nuxt#13949

❓ 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

We still have some information from Nuxt 2 docs in this section of the documentation. We can also consider removing this top-level key entirely (cc: @pi0) but as a first step we should remove the misleading docs.

📝 Checklist

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

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[pi0]

Removing docs is a good idea 👍🏼 If we can make generate deprecated with resolvers to infer wouldn't be also a bad idea, same as command, considering generate was a big feature of Nuxt 2 with lots of articles and examples using it.