Phone number not required in broadband portability isp info

CHANGELOG:

### Changed
- [#671](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/671) Phone number not required in broadband portability

Related card: https://trello.com/c/EMgFPH7Z/1050-permitir-crear-solicitud-adsl-portabilidad-sin-numero-de-telefono

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