fix notebook test

Author: blink1073

.github/workflows/downstream.yml

@@ -58,6 +58,8 @@ jobs:
     steps:
       - uses: actions/checkout@v2
       - uses: jupyterlab/maintainer-tools/.github/actions/base-setup@v1
-      - uses: jupyterlab/maintainer-tools/.github/actions/downstream-test@v1
-        with:
-          package_name: notebook>=7.0.0a5
+      - Name: Test notebook
+      - run: git clone https://github.com/jupyter/notebook.git
+          cd notebook
+          pip install -e ".[test]"
+          python -m pytest -ra -x -vv --full-trace --color=yes