[FIX] sale: error in computing SO reference

When processing a payment in Ecommerce, if the payment
acquirer communication is defined on 'Based on Document Reference'
and if the sale order sequence is having a suffix, we have
an internal error due to a bad implemented regexp.

opw-2067596
closes #36867

closes odoo/odoo#36892

X-original-commit: b08a0025
Signed-off-by: Nicolas Lempereur (nle) <nle@odoo.com>
Co-authored-by: Nicolas Lempereur <nle-odoo@users.noreply.github.com>