remove PaySheetModelLine_asPredicate script because it contains only "return context", and it's exactly what Predicate.asPredicate() returned if no script are found.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@27424 20353a03-c40f-0410-a6d1-a30d3c3de9de