[IMP] account: cash rounding: forbid entering a negative rounding value.

closes odoo/odoo#53312

X-original-commit: c4c1ba4a
Signed-off-by: Laurent Smet <smetl@users.noreply.github.com>
Signed-off-by: oco-odoo <oco-odoo@users.noreply.github.com>