Fix Faker version in gilab-ci

CHANGELOG:

### Fixed
- [#650](https://gitlab.com/coopdevs/odoo-somconnexio/-/merge_requests/650) Fix `Faker` version in gitlab-ci

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Avoid this error that is loaded from Faker 9.4.0 (https://github.com/joke2k/faker/commit/9a382ed237ef6ac40eb272703eb3b6ce0546ad0f)

2021-10-19 15:58:06,065 6225 ERROR openerp_test odoo.modules.registry: Failed to load registry
Traceback (most recent call last):
File "/usr/local/lib/python3.7/site-packages/faker/typing.py", line 5, in <module>
from typing import Literal  # type: ignore
ImportError: cannot import name 'Literal' from 'typing' (/usr/local/lib/python3.7/typing.py)

Avoid installing test dependencies in manifest, leaving them within the gitlab-ci