Update gunicorn requirement from <22.0,>=21.2 to >=22,<23 (#220)

* Update gunicorn requirement from <22.0,>=21.2 to >=21.2,<23.0

Updates the requirements on [gunicorn](https://github.com/benoitc/gunicorn) to permit the latest version.
- [Release notes](https://github.com/benoitc/gunicorn/releases)
- [Commits](benoitc/gunicorn@21.2.0...22.0.0)

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

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

* Cleanup dependency specifiers

---------

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Ed Morley <[email protected]>

Author: dependabot[bot]

Diff for: requirements.txt

@@ -1,7 +1,7 @@
 django>=5.0,<5.1
-gunicorn>=21.2,<22.0
-dj-database-url>=2.0,<3.0
-whitenoise[brotli]>=6.0,<7.0
+gunicorn>=22,<23
+dj-database-url>=2,<3
+whitenoise[brotli]>=6,<7
 
 # Uncomment these lines to use a Postgres database. Both are needed, since in production
 # (which uses Linux) we want to install from source, so that security updates from the