[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.
Pon mejor el `context` original, no `ctx`