Merge pull request #7920 from microsoft/dependabot/pip/tornado-6.5.5

Bump tornado from 6.5.4 to 6.5.5

Author: jenshnielsen

requirements.txt

@@ -427,7 +427,7 @@ toolz==1.1.0
     # via
     #   dask
     #   partd
-tornado==6.5.4
+tornado==6.5.5
     # via
     #   ipykernel
     #   jupyter-client