refactor(nuxt): use unref in fetch.ts

[yufanzheng0723]

🔗 Linked issue

❓ 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

change the isref of fetch.ts to unref

📝 Checklist

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

[codesandbox]

  Open in CodeSandbox Web Editor | VS Code | VS Code Insiders

[netlify]

✅ Deploy Preview for nuxt3-docs canceled.

Name	Link
🔨 Latest commit	f699cbd
🔍 Latest deploy log	https://app.netlify.com/sites/nuxt3-docs/deploys/63305f199bcf900008c56cdc