Notebook diff shows changes the extension doesn't make

[jrieken]

https://github.com/microsoft/vscode-github-issue-notebooks/blob/edf85a2e9db0d28166526c844e479724434209b6/src/extension/notebookProvider.ts#L271-L276

The pointer above shows what metadata the GH nb extension saves. The diff however, show all kinds of of things, like runState et al.

[jrieken]

This can likely be adjusted by fiddling with the transient options set but I think the diff should always go with what's stored on disk