Apparently Apple are switching out the tools used for notarizing things, so we need to adapt to the new way of doing things.
We got this warning from Apple:
> We’re reaching out because you recently used the altool command-line utility
> to notarize your macOS software with Apple. As announced last year at WWDC22,
> if you’re still using altool with the Apple notary service, you should
> transition to the notarytool command-line utility as soon as possible.
> Notarizing software with altool was deprecated in Xcode 13, and the Apple
> notary service will no longer accept uploads from altool as of November 1,
> 2023. Existing notarized software will continue to function properly.
> For information on notarizing your apps, read TechNote TN3147: Migrating to
> the latest notarization tool.