Bump gunicorn from 19.8.1 to 22.0.0

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 19.8.1 to 22.0.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@19.8.1...22.0.0)

---
updated-dependencies:
- dependency-name: gunicorn
  dependency-type: direct:production
...

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

requirements.txt

@@ -6,7 +6,7 @@ Django==3.2.24
 djangorestframework==3.11.2
 entrypoints==0.3
 flake8==3.7.9
-gunicorn==19.8.1
+gunicorn==22.0.0
 idna==3.7
 mccabe==0.6.1
 oauthlib==2.1.0