[forms] Do not raise errors on composite required relation being deleted
The entity included in the composite will be deleted in such a case, so
the field is not required even when the cardinality is '1' or '+'.
Related to #8529868
#! /bin/sh -e
#
if [ "$1" = remove -o "$1" = upgrade ]; then
if which install-docs >/dev/null 2>&1; then
install-docs -r cubicweb-doc
fi
fi
#DEBHELPER#
exit 0