[multi-sources-removal] Drop no more used federated ('true') multi-sources related code
Related to #2919300 (almost done!)
#! /bin/sh -e#if [ "$1" = configure ]; then if which install-docs >/dev/null 2>&1; then install-docs -i /usr/share/doc-base/cubicweb-doc fifi#DEBHELPER#exit 0