chore(deps): bump gunicorn in /tests/apps/python-flask

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 21.1.0 to 21.2.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](https://github.com/benoitc/gunicorn/compare/21.1.0...21.2.0)

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

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

tests/apps/python-flask/requirements.txt

@@ -1,5 +1,5 @@
 Flask==2.3.2
 Jinja2==3.1.2
 Werkzeug==2.3.6
-gunicorn==21.1.0
+gunicorn==21.2.0