[book] typos / clarifications in create-instance section Clarify that cubicweb-ctl upgrade needs to be run whenever cubicweb or a cube is upgraded. Related to #2632425.

#!/bin/sh -e
if [ "$1" = "purge" ] ; then
        update-rc.d cubicweb remove >/dev/null
fi
 
#DEBHELPER#
 
exit 0