fix: add redis to run tests

[YuriZmytrakov]

Description:

When running tests locally, in dev environement, we are encountering redis import error, because it is not being installed:

ImportError while loading conftest '/app/stac_fastapi/tests/conftest.py'.
conftest.py:16: in <module>
    from stac_fastapi.core.core import (
../core/stac_fastapi/core/core.py:27: in <module>
    from stac_fastapi.core.redis_utils import redis_pagination_links
../core/stac_fastapi/core/redis_utils.py:11: in <module>
    from redis import asyncio as aioredis
E   ModuleNotFoundError: No module named 'redis'

PR Checklist:

• Code is formatted and linted (run pre-commit run --all-files)
• Tests pass (run make test)
• Documentation has been updated to reflect changes, if applicable
• Changes are added to the changelog