[migration/3.21] fix stupid error in migration script
str.join doesn't like a list of ints. Closes #5706359.
#! /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