build(deps): bump google-cloud-storage from 2.18.2 to 3.1.0 in /backend

Bumps [google-cloud-storage](https://github.com/googleapis/python-storage) from 2.18.2 to 3.1.0.
- [Release notes](https://github.com/googleapis/python-storage/releases)
- [Changelog](https://github.com/googleapis/python-storage/blob/main/CHANGELOG.md)
- [Commits](googleapis/python-storage@v2.18.2...v3.1.0)

---
updated-dependencies:
- dependency-name: google-cloud-storage
  dependency-version: 3.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

Author: dependabot[bot]

backend/requirements.txt

@@ -4,7 +4,7 @@ datadog==0.51.0
 Flask==2.2.3
 Flask-Cors==6.0.0
 flask-talisman==1.1.0
-google-cloud-storage==2.18.2
+google-cloud-storage==3.1.0
 gunicorn==23.0.0
 python-dateutil==2.9.0.post0
 pytoml==0.1.21