Merge pull request #3125 from jupyterhub/dependabot/pip/images/hub/tornado-6.3.2

build(deps): bump tornado from 6.3.1 to 6.3.2 in /images/hub

Author: minrk

images/hub/requirements.txt

@@ -187,7 +187,7 @@ statsd==4.0.1
     # via -r requirements.in
 text-unidecode==1.3
     # via python-slugify
-tornado==6.3.1
+tornado==6.3.2
     # via
     #   jupyterhub
     #   jupyterhub-idle-culler