Katacode - stages interactive tutorial

[yevgenypats]

Bug Report

There is a bug in the stages tutorial https://katacoda.com/dvc/courses/get-started/stages, step-2 doesn't really work as
prepare.dvc is missing and probably dvc api was changed a bit so it is also expecting -n parameter which is not provided.

[shcheklein]

Closing this a duplicate treeverse/dvc.org#1586 . Sorry for the inconvenience, we are still in the process of updating our docs and tutorials after DVC 1.0 release.