chore(deps): bump gunicorn in /monitoring_flask_backend

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 25.1.0 to 25.3.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@25.1.0...25.3.0)

---
updated-dependencies:
- dependency-name: gunicorn
  dependency-version: 25.3.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

monitoring_flask_backend/requirements.txt

@@ -1,7 +1,7 @@
 Flask==3.1.3
 prometheus-api-client==0.5.4
 python-dateutil==2.9.0.post0
-gunicorn==25.1.0
+gunicorn==25.3.0
 requests==2.33.0
 pytest==9.0.2
 requests-aws4auth==1.3.1