Bump tornado from 6.3.3 to 6.4.1

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.3.3 to 6.4.1.
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.3.3...v6.4.1)

---
updated-dependencies:
- dependency-name: tornado
  dependency-type: direct:production
...

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

requirements.txt

@@ -90,7 +90,7 @@ termcolor==1.1.0
 terminado==0.8.2
 testpath==0.4.2
 thinc==7.1.1
-tornado==6.3.3
+tornado==6.4.1
 tqdm==4.66.3
 traitlets==4.3.3
 urllib3==1.26.18