build(deps): bump google-cloud-storage from 2.5.0 to 2.6.0 in /backend

Bumps [google-cloud-storage](https://github.com/googleapis/python-storage) from 2.5.0 to 2.6.0.
- [Release notes](https://github.com/googleapis/python-storage/releases)
- [Changelog](https://github.com/googleapis/python-storage/blob/main/CHANGELOG.md)
- [Commits](googleapis/python-storage@v2.5.0...v2.6.0)

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

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

Author: dependabot[bot]

backend/requirements.txt

@@ -5,7 +5,7 @@ fakeredis==1.9.1
 Flask==2.2.2
 Flask-Cors==3.0.10
 flask-talisman==1.0.0
-google-cloud-storage==2.5.0
+google-cloud-storage==2.6.0
 gunicorn==20.1.0
 python-dateutil==2.8.2
 pytoml==0.1.21