streamlit: fix build

pkgs/applications/science/machine-learning/streamlit/default.nix

···
 {   lib, buildPythonApplication, fetchPypi
   , altair, astor, base58, blinker, boto3, botocore, click, enum-compat
-  , future, pillow, protobuf, requests, toml, tornado, tzlocal, validators, watchdog
+  , future, pillow, protobuf, requests, toml, tornado_5, tzlocal, validators, watchdog
   , jinja2, setuptools
 }:
 
···
 
   propagatedBuildInputs = [
     altair astor base58 blinker boto3 botocore click enum-compat
-    future pillow protobuf requests toml tornado tzlocal validators watchdog
+    future pillow protobuf requests toml tornado_5 tzlocal validators watchdog
     jinja2 setuptools
   ];