Bump tornado from 6.5.4 to 6.5.5 (#570)

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.5.4 to 6.5.5.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.5.4...v6.5.5)

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

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Author: dependabot[bot]