Remove IsInPack product attribute

CHANGELOG:

### Remove
- [#nn](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/nn) Remove deprecated IsInPack product attribute.

Related card: https://trello.com/c/ZL7K1KhL/1693-eliminar-latribut-isinpack

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