[jupyterhub] remove outdated jupyter notebook options

jupyterhub/jupyter_notebook_config.py

-c.NotebookApp.open_browser = False
-c.NotebookApp.token = ''
 c.NotebookApp.allow_root = True
 c.NotebookApp.terminado_settings = { 'shell_command': ['/bin/bash', '-l'] }
 c.MultiKernelManager.default_kernel_name = 'robofish'