Add pip check

Author: krassowski

.github/workflows/job.test.yml

@@ -300,6 +300,9 @@ jobs:
       - name: Install python packages
         run: python -m pip install --find-links=dist --no-index --ignore-installed --no-deps jupyter_lsp jupyterlab_lsp
 
+      - name: Pip check
+        run: python -m pip check
+
       - name: List server extensions
         run: jupyter server extension list