Orfeo toolbox no longer available by default on Terrascope VMs

We will no longer provide Orfeo toolbox on the Terrascope user VMs because it was outdated, and very infrequently used.
Users who are still interested using Orfeo toolbox can easily install it as Docker image:
https://www.orfeo-toolbox.org/CookBook/Installation.html#docker-image