Merge pull request #3126 from jupyterhub/dependabot/pip/images/singleuser-sample/tornado-6.3.2

build(deps): bump tornado from 6.3.1 to 6.3.2 in /images/singleuser-sample

Author: minrk

images/singleuser-sample/requirements.txt

@@ -309,7 +309,7 @@ terminado==0.17.1
     #   notebook
 tinycss2==1.2.1
     # via nbconvert
-tornado==6.3.1
+tornado==6.3.2
     # via
     #   ipykernel
     #   jupyter-client