Remove jupyter_notebook_config.py

[mathbunnyru]

Describe your changes

Issue ticket if applicable

Checklist (especially for first-time contributors)

• I have performed a self-review of my code
• If it is a core feature, I have added thorough tests
• I will try not to use force-push to make the review process easier for reviewers
• I have updated the documentation for significant changes

[mathbunnyru]

@jtpio if that's ok I would like to ask you to take a look here as well.

After this change is merged, I will also try to update the documentation, where some options are passed (many examples use NotebookApp and give warnings currently) and I will tag you as well.

[jtpio]

Looks good thanks @mathbunnyru.

Notebook 7 should indeed be able to pick up jupyter_server_config.py.