We replaced provider with provider_interface to make it more clear to developers about provider api/backend being used. During that upgrade we removed support for mistral in provider to encourage developers to start using provider_interface. But this demo was not updated to use provider_interface as it was using mistral. This code change fixes it by replacing provider with provider_interface.
Signed-off-by: Adil Hafeez <adil.hafeez@gmail.com>