[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

version=3
opts=uversionmangle=s/(rc|a|b|c)/~$1/ \
http://pypi.debian.net/cubicweb/cubicweb-(.+)\.(?:zip|tgz|tbz|txz|(?:tar\.(?:gz|bz2|xz)))