Remove jupyter_notebook_config.json since notebook server is not supp…

…orted anymore (#1807)

* Move etc/jupyter/jupyter_notebook_config.json to etc/jupyter/jupyter_notebook_config.d/nbgrader.json

There is already jupyter_server_config.d/nbgrader.json and I don't see
why jupyter_notebook_config.json should be any different.

* Remove all instances of NotebookApp since the code requires Notebook >= 7

binder/jupyter_config.json

@@ -1,9 +1,5 @@
 {
   "ServerApp": {
     "root_dir": "example_course"
-  },
-  "NotebookApp": {
-    "notebook_dir": "example_course",
-    "root_dir": "example_course"
   }
 }

pyproject.toml

@@ -109,7 +109,6 @@ exclude = [
 
 [tool.hatch.build.targets.wheel.shared-data]
 "etc/jupyter/jupyter_server_config.d" = "etc/jupyter/jupyter_server_config.d"
-"etc/jupyter/jupyter_notebook_config.json" = "etc/jupyter/jupyter_notebook_config.json"
 "nbgrader/labextension/static" = "share/jupyter/labextensions/nbgrader/static"
 "install.json" = "share/jupyter/labextensions/nbgrader/install.json"
 "nbgrader/labextension/package.json" = "share/jupyter/labextensions/nbgrader/package.json"