Cleanup VRE Lab launcher

[dometto]

The JupyterLab environment you get when logging in to a VRE Lab instance can show a bunch of things other than notebooks: e..g OpenVSCode, RStudio, Desktop...

At present, these still show as 'Category: Notebook'. It would be nice if this was 'Other', or better yet, a custom category like 'Application'.

• Investigate this on a VRE Lab instance by editing the relevant jupyter config files.
• When it works, modify the jupyterhub_app role (or invocations of that role in playbooks)