Bump mysql-connector-python from 9.3.0 to 9.4.0 in /back-end

Bumps [mysql-connector-python](https://github.com/mysql/mysql-connector-python) from 9.3.0 to 9.4.0.
- [Changelog](https://github.com/mysql/mysql-connector-python/blob/trunk/CHANGES.txt)
- [Commits](mysql/mysql-connector-python@9.3.0...9.4.0)

---
updated-dependencies:
- dependency-name: mysql-connector-python
  dependency-version: 9.4.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

back-end/requirements.txt

@@ -18,5 +18,5 @@ uvicorn==0.35.0
 pytest==8.4.1
 pytest-cov==6.2.1
 mysql-connector==2.2.9
-mysql-connector-python==9.3.0
+mysql-connector-python==9.4.0
 ddt==1.7.2