chore(deps): bump tornado from 6.3.3 to 6.4 in /hack/api-docs (#3051)

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.3.3 to 6.4.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](https://github.com/tornadoweb/tornado/compare/v6.3.3...v6.4.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

hack/api-docs/requirements.txt

@@ -35,7 +35,7 @@ regex==2023.12.25
 requests==2.31.0
 six==1.16.0
 termcolor==2.4.0
-tornado==6.3.3
+tornado==6.4
 urllib3==2.1.0
 verspec==0.1.0
 watchdog==3.0.0