Drop support for macOS Catalina and earlier

[adamkpickering]

#3925 and #4999 have made it possible to disable upgrades of Rancher Desktop for systems that meet certain criteria. We have been holding back updates of certain components of Rancher Desktop so that it continues to work on macOS Catalina. This issue is about modifying the production Upgrade Responder config so that support is dropped for macOS Catalina and earlier, which will allow us to update the aforementioned components.