Upgrade jupyter-server to 2.20.

PiperOrigin-RevId: 945804026

Author: colaboratory-team

setup.py

@@ -24,7 +24,7 @@
     'ipyparallel==8.8.0',
     'ipython==7.34.0',
     'pandas==2.2.2',
-    'jupyter-server==2.18.2',
+    'jupyter-server==2.20.0',
     'portpicker==1.5.2',
     'requests==2.32.4',
     'tornado==6.5.7',