Bump gevent from 20.12.1 to 23.9.0

Bumps [gevent](https://github.com/gevent/gevent) from 20.12.1 to 23.9.0.
- [Release notes](https://github.com/gevent/gevent/releases)
- [Changelog](https://github.com/gevent/gevent/blob/master/docs/changelog_pre.rst)
- [Commits](gevent/gevent@20.12.1...23.9.0)

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

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

Author: dependabot[bot]

requirements.txt

@@ -16,7 +16,7 @@ Flask-SQLAlchemy==2.4.4
 Flask-Testing==0.8.1
 GeoAlchemy2==0.8.4
 geojson==2.5.0
-gevent==20.12.1
+gevent==23.9.0
 greenlet==0.4.17
 gunicorn==20.0.4
 hyperlink==20.0.1