[FIX] account: Unbalanced journal entries warning

Change of the error when a journal entries is unbalanced, so that the error is clearer for the user

closes odoo/odoo#102040

Task-id: 2999182
Signed-off-by: William André (wan) <wan@odoo.com>
Co-authored-by: maximilien(malb) <malb@odoo.com>
Co-authored-by: John Laterre (jol) <jol@odoo.com>