Remove handling of open source gpai models from check_excepted

[billmarinocam]

Since writing this code, I have learned that open source GPAI models must still abide by Article 53(1)(c) and 53(1)(d) -- in other words, it is not really an "exemption from the Act." It's more like a lighter list of requirements. So returning a message saying an exemption applies seems inaccurate.

As such, I'm not sure of the best way to fix this.

One idea is to create a new attribute in the project_cc named open_source_gpai_model. This could go under [gpai_model][open_source_gpai_model] in the project_cc for example. It could have its own corresponding variable in the dispositive variables that captures whether it is true, which happens when:

(project_cc_yaml['gpai_model']['gpai_model']['value'] == True and
project_cc_yaml['excepted']['open_source_gpai_model']['value'] == True and
dispositive_variables['ai_project_type']['gpai_model_systemic_risk'] == False)

If this value is True, then at some point in the analysis code, we make sure these requirements are met:

project_cc[gpai_model_obligations][other][policy] == true
project_cc[gpai_model_obligations][other][content] == true
project_cc[gpai_model_obligations][other][representative] == true

[billmarinocam]

Per discussion, Bill will take a pass at this one