Bump tornado from 6.5 to 6.5.5 in /docs

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.5 to 6.5.5.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.5.0...v6.5.5)

---
updated-dependencies:
- dependency-name: tornado
  dependency-version: 6.5.5
  dependency-type: indirect
...

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

Author: dependabot[bot]