fix(nuxt): only remove one item from middleware

[danielroe]

🔗 Linked issue

resolves #21701

❓ 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)
• 🧹 Chore (updates to the build process or auxiliary tools and libraries)
• ⚠️ Breaking change (fix or feature that would cause existing functionality to change)

📚 Description

An embarassing one - a misaligned bracket meant we were removing all middleware when <NuxtLoadingIndicator> was present. I've also added an extra test to ensure the added middleware is still present

📝 Checklist

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