build(deps): Bump redis from 3.3.11 to 3.4.1 in /backend

Bumps [redis](https://github.com/andymccurdy/redis-py) from 3.3.11 to 3.4.1.
- [Release notes](https://github.com/andymccurdy/redis-py/releases)
- [Changelog](https://github.com/andymccurdy/redis-py/blob/master/CHANGES)
- [Commits](redis/redis-py@3.3.11...3.4.1)

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

Author: dependabot-preview[bot]

backend/requirements.txt

@@ -9,6 +9,6 @@ google-cloud-storage==1.25.0
 gunicorn==20.0.4
 python-dateutil==2.8.1
 pytoml==0.1.21
-redis==3.3.11
+redis==3.4.1
 swagger-ui-bundle==0.0.6
 zstandard==0.13.0