[FIX] l10n_it_sdi_channel, l10n_it_fatturapa_pec: use the stored channel_id on attachment instead of the channel linked to the current company or channel on default company

[FIX] l10n_it_sdi_channel, l10n_it_fatturapa_pec: use the stored channel_id on attachment instead of the channel linked to the current company or channel on default company #9659