Update gunicorn requirement from <22,>=20 to >=20,<23 (#1073)

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@20.0.0...22.0.0)

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

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

Author: dependabot[bot]

requirements/adapter.txt

@@ -18,5 +18,5 @@ sanic>=22,<24; python_version>"3.6"
 starlette>=0.14,<1
 tornado>=6,<7
 uvicorn<1                                # The oldest version can vary among Python runtime versions
-gunicorn>=20,<22
+gunicorn>=20,<23
 websocket_client>=1.2.3,<2               # Socket Mode 3rd party implementation