kubeflow: TFMA plots don't render in JupyterLab but they work with Jupyter

See #1130

We broke the javascript widgets when we moved to mounting PVs under /home/jovyan

We fixed this in #1130 for Jupyter but its still broken for JupyterLab.

There was a previous issue when we originally did this about problems with JupyterLab. We should dig up that issue to see if its relevant.

Notebook reports error

Error loading widget . could not find model