Adapt to pack Sim Sending Letter Template

CHANGELOG:

### CHANGED
- [#871](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/871) Adapt to pack Sim Sending Letter Template

Related card: https://trello.com/c/1fisu7jf/1394-afegir-un-nou-template-o-modificar-lo-de-lenviament-de-sim-en-un-producte-pack-amb-2-m%C3%B2bils

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