fix(ContractHolderChangeWizard): Use available products
CHANGELOG:
### Fixed
- [#954](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/954) Use available_products instead of product_domain with Contract Change Tariff Wizard
Related card: https://trello.com/c/5lCNZTkj/1478-modificacions-al-wizard-canvi-de-titular
Edited by Gerard Funosas