build(deps): bump google-cloud-storage from 1.42.1 to 2.1.0 in /backend

Bumps [google-cloud-storage](https://github.com/googleapis/python-storage) from 1.42.1 to 2.1.0.
- [Release notes](https://github.com/googleapis/python-storage/releases)
- [Changelog](https://github.com/googleapis/python-storage/blob/main/CHANGELOG.md)
- [Commits](googleapis/python-storage@v1.42.1...v2.1.0)

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

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

Author: dependabot[bot]

backend/requirements.txt

@@ -5,7 +5,7 @@ fakeredis==1.7.0
 Flask==1.1.2
 Flask-Cors==3.0.10
 flask-talisman==0.8.1
-google-cloud-storage==1.42.1
+google-cloud-storage==2.1.0
 gunicorn==20.1.0
 python-dateutil==2.8.2
 pytoml==0.1.21