Bump tornado from 6.4.2 to 6.5.1 in /docs/sphinx (#1710)

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.4.2 to 6.5.1.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](https://github.com/tornadoweb/tornado/compare/v6.4.2...v6.5.1)

---
updated-dependencies:
- dependency-name: tornado
  dependency-version: 6.5.1
  dependency-type: indirect
...

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

docs/sphinx/requirements.txt

@@ -244,7 +244,7 @@ tabulate==0.9.0
     # via jupyter-cache
 tomli==2.0.1
     # via sphinx
-tornado==6.4.2
+tornado==6.5.1
     # via
     #   ipykernel
     #   jupyter-client