Remove hardcoded display number and port

In a multi-user environment, the display number and the port cannot
have to be selected based on what is available. For the display number,
vncserver uses the next free display number when unspecified. As for the
port number for websockify, we let jupyter-server-proxy logic finds one
for us.

jupyter_remote_desktop_proxy/__init__.py

@@ -40,7 +40,6 @@ def setup_desktop():
                 '-SecurityTypes',
                 'None',
                 '-fg',
-                ':1',
             ]
         )
     )
@@ -52,11 +51,10 @@ def setup_desktop():
             os.path.join(HERE, 'share/web/noVNC-1.2.0'),
             '--heartbeat',
             '30',
-            '5901',
+            '{port}',
         ]
         + socket_args
         + ['--', '/bin/sh', '-c', f'cd {os.getcwd()} && {vnc_command}'],
-        'port': 5901,
         'timeout': 30,
         'mappath': {'/': '/vnc_lite.html'},
         'new_browser_window': True,