[REQ] Delete orphaned models and tests from 2.0 samples

Created by: spacether

Is your feature request related to a problem? Please describe.

This is a general cleanup task

Describe the solution you'd like

When working on a python PR I noticed that the models animal_farm and string_boolean_map no longer exist in the 2.0 sample spec. Let's delete them from the the samples folder in the repo as they are no longer functional. https://github.com/OpenAPITools/openapi-generator/search?q=animalfarm&unscoped_q=animalfarm https://github.com/OpenAPITools/openapi-generator/search?q=stringbooleanmap&unscoped_q=stringbooleanmap

Describe alternatives you've considered

N/A

Additional context

This is just a nice to have update. Note: if we removed the models directories before writing the sample clients, we would have seen test errors and would have removed this outdated content.