build(deps): Bump python-dateutil from 2.8.0 to 2.8.1 in /backend

Bumps [python-dateutil](https://github.com/dateutil/dateutil) from 2.8.0 to 2.8.1.
- [Release notes](https://github.com/dateutil/dateutil/releases)
- [Changelog](https://github.com/dateutil/dateutil/blob/master/NEWS)
- [Commits](dateutil/dateutil@2.8.0...2.8.1)

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

Author: dependabot-preview[bot]

backend/requirements.txt

@@ -6,7 +6,7 @@ Flask-Cors==3.0.8
 flask-talisman==0.7.0
 google-cloud-storage==1.20.0
 gunicorn==19.9.0
-python-dateutil==2.8.0
+python-dateutil==2.8.1
 pytoml==0.1.21
 fakeredis==1.0.5
 redis==3.3.11