Make Jupyter-related docs cluster-agnostic
Now that JH is running on Rhino, we should remove the Crane-specific mentions and make the docs more general.
On Saturday, March 30 from 8:00 AM to 9:00 AM, we will be performing an upgrade of the GitLab system. During that time, GitLab and git services on git.unl.edu may be unavailable.
Now that JH is running on Rhino, we should remove the Crane-specific mentions and make the docs more general.