removed fixed tornado version (5.1.1) to allow Jupyter Lab 3

setup.py

@@ -25,7 +25,7 @@ setup(
         'jupyter',
         'jupyter-openbis-server>=0.1.4',
         'numpy',
-        'tornado==5.1.1',
+        'tornado',
     ],
     python_requires=">=3.3",
     classifiers=[