Bump pillow from 10.3.0 to 10.4.0 in /backend

Bumps [pillow](https://github.com/python-pillow/Pillow) from 10.3.0 to 10.4.0.
- [Release notes](https://github.com/python-pillow/Pillow/releases)
- [Changelog](https://github.com/python-pillow/Pillow/blob/main/CHANGES.rst)
- [Commits](python-pillow/Pillow@10.3.0...10.4.0)

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

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

backend/requirements.txt

@@ -71,7 +71,7 @@ jsonschema-specifications==2023.12.1
     # via jsonschema
 packaging==24.1
     # via gunicorn
-pillow==10.3.0
+pillow==10.4.0
     # via -r requirements.in
 psycopg==3.2.1
     # via -r requirements.in