Bump requests from 2.27.1 to 2.28.0 in /backend

Bumps [requests](https://github.com/psf/requests) from 2.27.1 to 2.28.0.
- [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...v2.28.0)

---
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

@@ -6,7 +6,7 @@ python-engineio==3.14.2
 python-socketio==4.6.1
 six==1.16.0
 pytest==7.1.2
-requests==2.27.1
+requests==2.28.0
 discord-webhook==0.16.3
 datadog==0.44.0
 ddtrace==1.1.4