build(deps): bump redis from 4.5.1 to 5.0.0 in /backend

Bumps [redis](https://github.com/redis/redis-py) from 4.5.1 to 5.0.0.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v4.5.1...v5.0.0)

---
updated-dependencies:
- dependency-name: redis
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/requirements.txt

@@ -8,6 +8,6 @@ google-cloud-storage==2.7.0
 gunicorn==20.1.0
 python-dateutil==2.8.2
 pytoml==0.1.21
-redis==4.5.1
+redis==5.0.0
 swagger-ui-bundle==0.0.9
 zstandard==0.21.0