Auto-detected frameworks detects Next.js with no Next.js app in monorepo

### Environment information

```plain text
npm error could not determine executable to run
npm error A complete log of this run can be found in: /home/ty/.npm/_logs/2024-05-30T13_26_34_967Z-debug-0.log
```

### Description

I do not have a Next.js app in my monorepo, Amplify Gen2 "auto-detects" Next.js whenever I select the app I want to deploy.


No source files, tests, or entry points are identified in the issue. First reproduce auto-detection with a monorepo that has no Next.js app and inspect the detection flow; done means Amplify no longer selects Next.js for that repository while still detecting an actual Next.js app.

Written by the indexing model from the issue text.