docs(config): fix setResponseHeader example params

[metowolf]

🔗 Linked issue

none

❓ Type of change

• 📖 Documentation (updates to the documentation, readme, or JSdoc annotations)
• 🐞 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

https://github.com/unjs/h3/blob/53703dc860f1ff6fe7ce71d543deff1cfa810b11/src/utils/response.ts#L120

cause error

[nitro] [unhandledRejection] TypeError: Cannot read properties of undefined (reading 'res')
    at setResponseHeader (file:///data/workspace/node_modules/.pnpm/h3@1.9.0/node_modules/h3/dist/index.mjs:730:14)
    at file:///data/workspace/.nitro/dev/index.mjs:512:3
    at Object.onError (file:///data/workspace/.nitro/dev/index.mjs:552:14)
    at Server.toNodeHandle (file:///data/workspace/node_modules/.pnpm/h3@1.9.0/node_modules/h3/dist/index.mjs:1892:27)
    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)

📝 Checklist

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

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