Bump gunicorn from 20.1.0 to 22.0.0 in /requirements

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 20.1.0 to 22.0.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@20.1.0...22.0.0)

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

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

Author: dependabot[bot]

requirements/production.txt

@@ -5,6 +5,6 @@ gevent==20.9.0
 greenlet==0.4.17
 raven==6.10.0
 redis==3.5.3
-gunicorn==20.1.0
+gunicorn==22.0.0
 hiredis==2.0.0
 sentry-sdk==1.5.12