fix: correct test for isFullStatic in legacy composition api

[wattanx]

🔗 Linked issue

#730

❓ 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

In the case of nuxt start, process.static always seems to be true. Therefore, it generates global.mjs like @nuxtjs/composition-api and outputs isFullStatic.

📝 Checklist

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