Update example Terraform plans to Juju Terraform provider >= 1.0

[NucciTheBoss]

The first stable version of the Juju Terraform provider, version 1.0, was released back in October during the Canonical Engineering Sprint. A breaking change introduced in version 1 of the provider is that model_name is no longer a passable parameter to the juju_application resource. The model_name parameter has been superseded by the model_uuid parameter.

We'll need to update our existing Terraform examples to use the 1.0 version of the provider, otherwise we're going to have a lot of unhappy cluster administrators.