Bump gevent from 21.1.2 to 21.12.0

Bumps [gevent](https://github.com/gevent/gevent) from 21.1.2 to 21.12.0.
- [Release notes](https://github.com/gevent/gevent/releases)
- [Changelog](https://github.com/gevent/gevent/blob/master/docs/changelog_pre.rst)
- [Commits](gevent/gevent@21.1.2...21.12.0)

---
updated-dependencies:
- dependency-name: gevent
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

requirements.txt

@@ -31,7 +31,7 @@ flask==1.1.4
     #   sentry-sdk
 flask-wtf==0.15.1
     # via -r requirements.in
-gevent==21.1.2
+gevent==21.12.0
     # via -r requirements.in
 greenlet==1.1.0
     # via gevent