Bump tornado from 6.1 to 6.4

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.1 to 6.4.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.1.0...v6.4.0)

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

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

requirements.txt

@@ -2,7 +2,7 @@ voluptuous==0.12.2
 PyYAML==5.4.1
 paho-mqtt==1.5.1
 colorama==0.4.4
-tornado==6.1
+tornado==6.4
 tzlocal==3.0    # from time
 tzdata>=2021.1  # from time
 pyserial==3.5