Steps to Reproduce:

1. Install previous version of vscode
2. Remove /etc/apt/sources.list.d/vscode.list
3. Create /etc/apt/sources.list.d/vscode.sources
4. Upgrade vscode and see that now vscode.list and vscode.sources exist
5. apt is now broken

I don't think the postinst script should be responsible for managing vscode.list.

Another option would be to support DEB822 when it is detected... or at least not interfere with it.