Bump tornado from 6.4 to 6.4.2 in /benchmarks/django-workers

Bumps [tornado](https://github.com/tornadoweb/tornado) from 6.4 to 6.4.2.
- [Changelog](https://github.com/tornadoweb/tornado/blob/v6.4.2/docs/releases.rst)
- [Commits](tornadoweb/tornado@v6.4.0...v6.4.2)

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

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

benchmarks/django-workers/requirements.txt

@@ -182,7 +182,7 @@ stripe==7.11.0
 text-unidecode==1.3
 timeago==1.0.16
 tinycss2==1.2.1
-tornado==6.4
+tornado==6.4.2
 tqdm==4.66.1
 traitlets==5.14.1
 twilio==8.11.0