Disable RTC on stat159 hub

https://uctech.slack.com/archives/CC3NKQA3B/p1646276416672839
@fperez encountered serious data corruption bugs, that
we suspect is caused by enabling collaborative editing.
Let's turn it off and see if it goes away?

deployments/stat159/config/common.yaml

@@ -39,10 +39,6 @@ jupyterhub:
       # Tell code where to display GUIs
       # The VNC /desktop link must be opened already for this to work
       DISPLAY: ":1.0"
-    # Enable RTC and jupyterlab-link-share
-    cmd:
-    - jupyterhub-singleuser
-    - --LabApp.collaborative=true
     extraFiles:
       lab-config:
         data: