[FIX] account_xunnel, invoice_xunnel: Since xunnel token, testing, last t#35511

sycn are related fields, they don't need to be explicitly set or get, for example field tax_cash_basis_journal_id on account module https://github.com/odoo/odoo/blob/d34d6867f2ff9abdf303f12b3fb9b7fc20e709ab/addons/account/models/res_config_settings.py

We this, we pretend to dismiss the problem with those fields that being cleaned after each production update.