[jupyterhub] remove ssh

jupyterhub/base/Dockerfile

@@ -85,11 +85,6 @@ RUN mkdir -p /usr/local/venv && \
         && \
     ipython kernel install --name=default
 
-RUN apt-get update && \
-    apt-get install -y \
-        ssh && \
-    apt-get clean
-
 RUN chmod -x /etc/update-motd.d/*
 
 WORKDIR "${HOME}"