Fix contract terminate user reason table reference

CHANGELOG:

### Fixed
- [#622](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/622) Fix contract terminate user reason table reference

Related card: https://trello.com/c/nqM05yX7/952-fix-motius-finalitzaci%C3%B3-contracte-per-canvi-titular

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