[FIX] account_edi_ubl_cii: ubl2.0 import tax retrieving

During the work done on OIOUBL einvoice import, we saw that the
`Percent` node is always located below a `TaxCategory` node in UBL 2.0.

Task-id: 3420748
X-original-commit: 71d8bf93be472bdcf232e25e42f818e2df89cf8b
Part-of: odoo/odoo#137758

addons/account_edi_ubl_cii/models/account_edi_xml_ubl_20.py

@@ -735,7 +735,7 @@ class AccountEdiXmlUBL20(models.AbstractModel):
         tax_nodes = tree.findall('.//{*}Item/{*}ClassifiedTaxCategory/{*}Percent')
         if not tax_nodes:
             for elem in tree.findall('.//{*}TaxTotal'):
-                tax_nodes += elem.findall('.//{*}TaxSubtotal/{*}Percent')
+                tax_nodes += elem.findall('.//{*}TaxSubtotal/{*}TaxCategory/{*}Percent')
         return self._import_fill_invoice_line_taxes(tax_nodes, invoice_line, inv_line_vals, logs)
 
     def _correct_invoice_tax_amount(self, tree, invoice):