Upgrades OkHttp to version 4.7.2 and Retrofit to 2.9.0
Resolves issues caused in CI due to conflicting OkHttp versions.
* What went wrong:
Execution failed for task ':modules:testapp:MyTestApp:appCenterUploadDebug'.
> okhttp3.internal.platform.Platform.log(ILjava/lang/String;Ljava/lang/Throwable;)V
Upgrades OkHttp to version 4.7.2 and Retrofit to 2.9.0
Resolves issues caused in CI due to conflicting OkHttp versions.