Bump requests from 2.27.1 to 2.28.2 in /backend

Bumps [requests](https://github.com/psf/requests) from 2.27.1 to 2.28.2.
- [Release notes](https://github.com/psf/requests/releases)
- [Changelog](https://github.com/psf/requests/blob/main/HISTORY.md)
- [Commits](https://github.com/psf/requests/compare/v2.27.1...v2.28.2)

---
updated-dependencies:
- dependency-name: requests
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

@@ -6,6 +6,6 @@ python-engineio==3.14.2
 python-socketio==4.6.1
 six==1.16.0
 pytest==7.2.0
-requests==2.27.1
+requests==2.28.2
 discord-webhook==0.15.0
 datadog==0.44.0