fix(devtools): remove cjs entrypoint

[danielroe]

🔗 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)
• ✨ 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

discovered in https://github.com/nuxt/ecosystem-ci/actions/runs/11286607655/job/31391242329, it seems that with new jiti upgrade we are loading the cjs version of devtools in the prepare step, which is flagging up an issue (this.nuxt doesn't work as this isn't defined) - cc: @pi0 in case this isn't expected

note, even this?.nuxt doesn't work as the dynamic import of ./dist/module.mjs doesn't work in the prepare step (before dist/module.mjs has been stubbed out)

I think it's safe to remove the cjs stub as it shouldn't be loaded by nuxt but you may have more context.

[antfu]

As we requires Nuxt v3.9, I agree that cjs entry shouldn't be needed at all. Just in case any, I will release this as a minor.