Bump gunicorn from 20.0.4 to 22.0.0 (#101)

Bumps [gunicorn](https://github.com/benoitc/gunicorn) from 20.0.4 to 22.0.0.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@20.0.4...22.0.0)

---
updated-dependencies:
- dependency-name: gunicorn
  dependency-version: 22.0.0
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

requirements.txt

@@ -5,6 +5,6 @@ Markdown==3.2.1
 coreapi==2.3.3
 psycopg2-binary==2.8.4
 dj-database-url==0.5.0
-gunicorn==20.0.4
+gunicorn==22.0.0
 whitenoise==5.0.1
 PyYAML==6.0.2