the android flavor document is incorrect

### Page URL

https://docs.flutter.dev/deployment/flavors/

### Page source

https://github.com/flutter/website/tree/main/src/content/deployment/flavors.md

### Describe the problem

I'm not familiar with build flavors or Kotlin, and I tried to follow the documentation, but it is incorrect. Even the code provided at the first stage—along with the instructions to run the build to launch the application and verify everything—contains syntax issues and does not work.

If something needs to be filled in, what is it? If something is missing, what exactly is missing?

The sample code and instructions don't work. Moreover, the build.gradle.kts file in the latest Flutter project is different from what is mentioned in the documentation.

### Expected fix

being able to follow the documentation without any issue

### Additional context

_No response_

### I would like to fix this problem.

- [ ] I will try and fix this problem on docs.flutter.dev.