Bump tornado from 6.4 to 6.4.1 in /docs

Bumps [tornado](https://github.com/tornadoweb/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
...

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

docs/requirements.txt

@@ -74,7 +74,7 @@ soupsieve==2.5
 stack-data==0.6.3
 tinycss2==1.2.1
 toml==0.10.2
-tornado==6.4
+tornado==6.4.1
 traitlets==5.14.2
 urllib3==2.2.1
 watchdog==4.0.0