Update gunicorn to 21.2.0

[pyup-bot]

This PR updates gunicorn from 20.1.0 to 21.2.0.

Changelog

21.2.0

===================

- fix thread worker: revert change considering connection as idle . 

*** NOTE ***

This is fixing the bad file description error.

21.0.1

===================

- fix documentation build

21.0.0

===================

- support python 3.11
- fix gevent and eventlet workers
- fix threads support (gththread): improve performance and unblock requests
- SSL: noaw use SSLContext object
- HTTP parser: miscellaneous fixes
- remove unecessary setuid calls
- fix testing
- improve logging
- miscellaneous fixes to core engine

*** RELEASE NOTE ***

We made this release major to start our new release cycle. More info will be provided on our discussion forum.

Links

• PyPI: https://pypi.org/project/gunicorn
• Changelog: https://pyup.io/changelogs/gunicorn/
• Homepage: https://gunicorn.org