Bump tornado from 6.4 to 6.4.1 in the pip group

Bumps the pip group with 1 update: [tornado](https://github.com/tornadoweb/tornado).


Updates `tornado` from 6.4 to 6.4.1
- [Changelog](https://github.com/tornadoweb/tornado/blob/master/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.4.0...v6.4.1)

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

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

requirements.txt

@@ -79,7 +79,7 @@ six==1.16.0
 soupsieve==2.5
 stack-data==0.6.3
 tinycss2==1.3.0
-tornado==6.4
+tornado==6.4.1
 traitlets==5.14.3
 wakepy==0.9.1
 wcwidth==0.2.13