[FIX] account: fix help tooltip

The pro-forma state doesn't exist anymore on invoices

addons/account/models/account_invoice.py

@@ -228,7 +228,6 @@ def _compute_payments(self):
         ], string='Status', index=True, readonly=True, default='draft',
         track_visibility='onchange', copy=False,
         help=" * The 'Draft' status is used when a user is encoding a new and unconfirmed Invoice.\n"
-             " * The 'Pro-forma' status is used when the invoice does not have an invoice number.\n"
              " * The 'Open' status is used when user creates invoice, an invoice number is generated. It stays in the open status till the user pays the invoice.\n"
              " * The 'Paid' status is set automatically when the invoice is paid. Its related journal entries may or may not be reconciled.\n"
              " * The 'Cancelled' status is used when user cancel invoice.")