build(deps): bump redis from 5.0.1 to 5.0.4 in /backend (#2299)

Bumps [redis](https://github.com/redis/redis-py) from 5.0.1 to 5.0.4.
- [Release notes](https://github.com/redis/redis-py/releases)
- [Changelog](https://github.com/redis/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@v5.0.1...v5.0.4)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

backend/requirements.txt

@@ -8,6 +8,6 @@ google-cloud-storage==2.16.0
 gunicorn==22.0.0
 python-dateutil==2.8.2
 pytoml==0.1.21
-redis==5.0.1
+redis==5.0.4
 swagger-ui-bundle==1.1.0
 zstandard==0.22.0