Update jupyterlab_server dependency

setup.py

@@ -146,7 +146,7 @@ setup_args['install_requires'] = [
     'packaging',
     'tornado!=6.0.0, !=6.0.1, !=6.0.2',
     'jupyter_core',
-    'jupyterlab_server~=2.0.0rc3',
+    'jupyterlab_server~=2.0.0rc5',
     'jupyter_server~=1.0.1',
     'nbclassic~=0.2.0',
     'jinja2>=2.10'