accounting: keep "??? (value)" to display invalid bank account
The changes from ae15e7e1 (accounting: show the context when showing invalid bank accounts, 2022-12-21) were a regression because with the previous behaviour, by just looking at the transactions, users could see with the ??? that something was wrong with the bank account. After these changes they had to open the select element.
This restore somehow the previous behaviour by displaying the label with ??? marker, but since we have the label, we display the label (bank account reference) instead of the value (the relative URL)