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](https://github.com/tornadoweb/tornado/compare/v6.3.3...v6.4.1)

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

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

Pipfile

@@ -56,7 +56,7 @@ sqlparse = "~=0.5.0"
 static3 = "~=0.7.0"
 svg2rlg = "~=0.3"
 tini = "~=3.0.1"
-tornado = "~=6.3"
+tornado = "~=6.4"
 urllib3 = "~=1.26.19"
 whitenoise = "~=5.2.0"
 yolk = "~=0.4.3"