Revert "[FIX] Use unique accounts and improved bank search in base."

This reverts commit 5538c234d9.

account_bank_statement_import/res_partner_bank.py

@@ -64,8 +64,3 @@ class ResPartnerBank(models.Model):
         return super(ResPartnerBank, self).search(
             cr, user, args, offset=offset, limit=limit, order=order,
             context=context, count=count)
-
-    _sql_constraints = [
-        ('unique_number', 'unique(sanitized_acc_number)',
-         'Account Number must be unique'),
-    ]