do not allow to change the section at line level, it is too confusing and...

do not allow to change the section at line level, it is too confusing and would require line level security

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@34505 20353a03-c40f-0410-a6d1-a30d3c3de9de