Bump version 12.0.2.1.6

CHANGELOG:

## [12.0.2.1.6] - 2023-02-27
### Fixed
- [#1000](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/1000) Send subdivision code to OTRS without the country code.
- [#994](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/994) Fix contract holder change available products: filter by old product category

### Changed
- [#997](https://git.coopdevs.org/coopdevs/som-connexio/odoo-somconnexio/-/merge_requests/997) When changing a contract's holder, the new contract should start one day after the end date from the old one.

Related card: https://trello.com/c/Eeu2xpKz/1580-template-release-120216

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