l10n_it_edi: can't import multiple invoices from the same XML

[Lorenzo Battistini]

Impacted versions:

• 17.0

Steps to reproduce:

Import an XML with 2 invoices, like the following

https://github.com/OCA/l10n-italy/blob/ca7762b5978b7aa4b4d6e89148d32ea54d4e0414/l10n_it_fatturapa_in/tests/data/IT01234567890_FPR03.xml

Current behavior:

1 invoice is created

Expected behavior:

2 invoices are created

Video/Screenshot link: