Remove custom filter wizard current tariff

CHANGELOG:

### Removed
- [#657](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/657) Hide `tariff_product` field in contract custom search

Related card: https://trello.com/c/3w5DIdMr/995-filtre-sobre-tarifa-actual-a-contractes-no-funciona

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