[FIX] account: revert commit f607572d

This case of amls having a zero balance but an amount in foreign currency left is already managed by the new reconciliation in 16.0.
Furthermore:
-the test in POS is passing even with the revert
-the reverted commit introduces a performance issue on amount_residual by forcing the orm to fetch the whole m2m debit/credit_matched_ids.
-there is no test accounting-side depicting the issue (if there is really an issue fixed by the commit).

Part-of: odoo/odoo#111962