Can't build flutter app

I’m new to flutter and want to integrate Auth0 universal login by following this tutorial.Auth0 Flutter SDK Quickstarts: Add login to your Flutter app. However, I got stuck on the build step, as I consistently hit the error says, I need latest version.

But for the latest flutter setup, there’s no ext.kotlin_version = '<latest-version>' in C:\dev\demo\android\build.gradle. Wonder if I can get some help with it. Thanks.