Updated the "XGBoost Trainer'" sample (#1116)
Updated the "XGBoost Trainer'" sample (#1116)

* Updated the "XGBoost Trainer'" sample
Modernized the sample pipeline code.

* Added a note about enabling Dataproc API

kubeflow/pipelines,kubeflow/pipelines,kubeflow/pipelines,kubeflow/pipelines,kubeflow/pipelines,kubeflow/pipelines