[FIX] account: fixed typo in backport of fix of generation of...

[FIX] account: fixed typo in backport of fix of generation of account.move.lines from invoice by providing extension hook

lp bug: https://launchpad.net/bugs/452854 fixed

bzr revid: odo@openerp.com-20100430123401-wfns09pk00z0qiyr