[FIX] l10n_be_invoice_bba: constraint _check_communication

The constraint checks a non-existant field 'Communication'.
Should be 'reference' and 'reference_type'

Closes #9739

addons/l10n_be_invoice_bba/invoice.py

@@ -227,7 +227,7 @@ class account_invoice(osv.osv):
             required=True, readonly=True),
     }
     _constraints = [
-        (_check_communication, 'Invalid BBA Structured Communication !', ['Communication']),
+        (_check_communication, 'Invalid BBA Structured Communication !', ['reference', 'reference_type']),
         ]
 
 account_invoice()