Fix broken Gradle Sync when opening the project with Android Studio (#39412)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/39412

This fixes an issue that I got reported by users attempting to open the react-native GitHub project in Android Studio.

The error is:
```
  Cannot specify include directories for target "react_codegen_AppSpecs" which is  not built by this project.
```

Changelog:
[Internal] [Changed] - Fix broken Gradle Sync when opening the project with Android Studio

Reviewed By: huntie

Differential Revision: D49189331

fbshipit-source-id: 632063a7e1afc53284231be263bec352dc7057c5