docs: simplify android setup (#85)

Author: vonovak

docs/setting-up/android.md

@@ -52,7 +52,3 @@ This ends the setup for Firebase.
 ## Rebuild the native project
 
 Do not forget to rebuild the native app after the setup is done.
-
-## Choose Dependency versions (optional)
-
-The library depends on `com.google.android.gms:play-services-auth`, as seen in [build.gradle](https://github.com/react-native-community/google-signin/blob/master/android/build.gradle). If needed, you may control their versions by the `ext` closure, as seen in the code snippet above.

docs/troubleshooting.md

@@ -39,10 +39,6 @@ See [`DEVELOPER_ERROR` paragraph](#developer_error).
 
 See [this comment](https://github.com/react-native-community/google-signin/issues/659#issuecomment-513555464). Or [this SO question](https://stackoverflow.com/questions/53816227/google-signin-sdk-is-failing-by-throwing-error-a-non-recoverable-sign-in-failur).
 
-### Changing `play-services-auth` version
-
-See ["Choose Dependency versions"](setting-up/android.md#choose-dependency-versions-optional) above.
-
 ### Package name !== application id
 
 When adding a new oauth client, google asks you to add your package name. In some cases your package name is not equal to your application id. Check if your package name in the `AndroidManifest.xml` is the same as your application/bundle id. Find your application id in the play console or `android/app/build.gradle`. The format looks like `com.yourapp.id`.