[FIX] Fix for error on invoice validation using account_invoice_sequence

The module l10n_es_account_invoice_sequence gives me the following error:

File "/opt/openerp/v7/spain/l10n_es_account_invoice_sequence/account_invoice.py", line 71, in action_number
    context=context)
TypeError: action_number() got an unexpected keyword argument 'context'

This commit fix the error for me.

More info at: https://groups.google.com/forum/#!msg/openerp-spain-users/Znh1SS3HiTo/zVvQIhB9CCUJ

NOTE*) Prior pull request failed to build on Travis because a missing space. This commit adds it.
No había visto este mail :) Si solo es cambiar ctx por context ahí llegamos… :P
> El 8/8/2014, a las 11:51, Pedro M. Baeza <notifications@github.com> escribió:
> 
> In l10n_es_account_invoice_sequence/account_invoice.py:
> 
> > @@ -67,8 +67,7 @@ def action_number(self, cr, uid, ids, context=None):
> >              number = sequence_obj.get_id(cr, uid, sequence.id, context=ctx)
> >              self.write(cr, uid, [invoice.id], {'number': number},
> >                         context=context)
> > -        result = super(AccountInvoice, self).action_number(cr, uid, ids,
> > -                                                           context=context)
> > +        result = super(AccountInvoice, self).action_number(cr, uid, ids, ctx)
> Pon mejor el context original, no ctx
> 
> —
> Reply to this email directly or view it on GitHub <https://github.com/OCA/l10n-spain/pull/47/files#r15985370>.
>