Set end date to false in Partner if is coop candidate or member
CHANGELOG:
### Fixed
- [#nn](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/nn) Set cooperator_end_date empty in Partner if is coop_candidate or member
We need to remove the cooperator end date in case of member or cooperator candidate to avoid confusion with the old members that renew the membership.
- Old member:
- Old member with SR validated: