Add Sonatype Central repository for users of nightly builds only (#55305)

Summary:
Even though Sonatype Central repository isn't used by an app, still the React Native Gradle plugin adds the Sonatype Central to repositories.
In some cases it leads to a considerable amount of failed requests on Gradle downloading dependencies.

<img width="1076" height="109" alt="858 failed requests out of 858 requests" src="https://github.com/user-attachments/assets/40d6aeb6-dcc4-4ebb-9f0b-742d26ba6e65" />

I'm introducing a change where Sonatype Central repository is included for users of nightly builds only.

## Changelog:

[ANDROID] [CHANGED] - Add Sonatype Central repository for users of nightly builds only

Pull Request resolved: https://github.com/facebook/react-native/pull/55305

Test Plan:
All of the tests in gradle plugin are green
```
$ ./gradlew test

BUILD SUCCESSFUL in 10s
20 actionable tasks: 20 executed
```

Reviewed By: cipolleschi

Differential Revision: D91887976

Pulled By: cortinico

fbshipit-source-id: 1e61d3b8d97a444e17a02bfe9ed0334e9b0ab0bc