Bump tornado from 6.3.3 to 6.4.2

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.3.3 to 6.4.2.
- [Changelog](https://github.com/tornadoweb/tornado/blob/v6.4.2/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.3.3...v6.4.2)

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

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

requirements.txt

@@ -3,7 +3,7 @@ pymongo==4.6.3
 mongomock==4.0.0
 mongomock-motor==0.0.14
 montydb==2.4.0
-tornado==6.3.3
+tornado==6.4.2
 motor==3.0.0
 pytest==7.0.1
 pytest-cov==3.0.0