[FIX] sale: Partial payment link with invoice policy based on deliverd qty

- Configure payment stripe to be available on the web shop
- Let's consider a product with P (sales price = 100€) invoice policy based on delivered qty
- Set in the config parameter sale.automatic_invoice to True
- Create a SO with P and generate a payment link PL for 50€
- Go to PL and pay it

Bug:

An error was raised because there was no invoicable line when computing the
invoice of SO

opw:2635175

closes odoo/odoo#75892

Signed-off-by: Simon Goffin (sig) <sig@openerp.com>