Bump eventlet from 0.31.0 to 0.40.3

Bumps [eventlet](https://github.com/eventlet/eventlet) from 0.31.0 to 0.40.3.
- [Changelog](https://github.com/eventlet/eventlet/blob/master/NEWS)
- [Commits](eventlet/eventlet@v0.31.0...0.40.3)

---
updated-dependencies:
- dependency-name: eventlet
  dependency-version: 0.40.3
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,7 +1,7 @@
 astroid==2.4.2
 click==7.1.2
 dnspython==1.16.0
-eventlet==0.31.0
+eventlet==0.40.3
 Flask==1.1.2
 Flask-SocketIO==4.3.1
 greenlet==0.4.17