Deduce from credit amount only sales from the user's company

Since #4080 the record rules are no more enforced on getter of Function
fields.

Closes #12586
(grafted from 27f9dfa253e48fd885ea54d5b983186d7e829583)

--HG--
branch : 6.0

modules/sale_credit_limit/party.py

@@ -25,6 +25,7 @@ class Party(metaclass=PoolMeta):
         currency = user.company.currency
 
         sales = Sale.search([
+                ('company', '=', user.company.id),
                 ('party', 'in', [p.id for p in parties]),
                 ('state', 'in', ['confirmed', 'processing']),
                 ])