Don't chown -R a user's home directory

Only the top level permissions are set wrong due to kubernetes not being able to do this automatically.

This hits significant problems when the chown takes more than 30s and the pod fails to start

base-notebook/start.sh

@@ -40,7 +40,7 @@ if [ $(id -u) == 0 ] ; then
     # Ex: default NFS/EFS (no auto-uid/gid)
     if [[ "$CHOWN_HOME" == "1" || "$CHOWN_HOME" == 'yes' ]]; then
         echo "Changing ownership of /home/$NB_USER to $NB_UID:$NB_GID"
-        chown -R $NB_UID:$NB_GID /home/$NB_USER
+        chown $NB_UID:$NB_GID /home/$NB_USER
     fi
 
     # handle home and working directory if the username changed