[hooks] Skip modification_date attribute in "notifentityupdated" hook Depending on the call order of hooks, "modification_date" may come in entity.cw_edited or not (from "metaattrsupdate" hook usually). It should however not be considered in the notification context. Closes #8842064.

usr/lib/python2*/*-packages/cubicweb/entities/
usr/lib/python2*/*-packages/cubicweb/ext/
usr/share/cubicweb/cubes/
usr/lib/python2*/*-packages/cubicweb/*.py