chore: Bump gevent from 21.1.2 to 23.9.0 in /load_tests

Bumps [gevent](https://github.com/gevent/gevent) from 21.1.2 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@21.1.2...23.9.0)

---
updated-dependencies:
- dependency-name: gevent
  dependency-type: indirect
...

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