Inline response schemas with additionalProperties with boolean values are no longer ignored

[twof]

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Description of the PR

This is meant to be released in the next v2.4.x release. It's branched off of the v2.4.10 tag. This PR resolves #9885

My understanding is that additionalProperties fields with boolean values should be ignored, as they are not explicitly in or against the OpenAPI 2/3 spec. However in the current V2.4.x and v3.0.x releases, if an additionalProperties field with a boolean value is contained within an inline response schema, the response model is never added to the list of definitions on swagger.definitions which causes swagger-codegen to fail to generate it.

That is because they're treated as UntypedProperty which previously wasn't a handled case. This PR adds a case for additionalProperties to be an UntypedProperty, and effectively ignores the value of additionalProperties.

Let me know if yall (the maintainers) think this is a good solution or if you have any additional feedback. Java isn't my primary language, so apologies if I've broken conventions.

Thanks!

(details of the change, additional tests that have been done, reference to the issue for tracking, etc)
#9885