PyRIT v0.7.0 change to model_name breaks PyRIT-Ship

PyRIT's v0.7.0 switch from deployment_name to model_name broke the initialize_chat_target() function since it still used the deployment_name parameter.  I have a code fix to use model_name instead and will open a PR for that, just posting for awareness.

Also @jorisdg I saw your comment in the other issue, I'll shoot you an email soon.