[IMP] account: do not grep partners for statement matching

Doing a regex search forces a sequential scan on too many rows.
Because this is a function called often during the bank reconciliation,
it is better to prioritize a faster flow than an automatic detection that is
likely to not return anything anyways.

closes odoo/odoo#105347

Related: odoo/enterprise#33772
Signed-off-by: William André (wan) <wan@odoo.com>