[BUG] Query param content type does not pass validation

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
• Have you search for related issues/PRs?
• What's the actual output vs expected output?
• [Optional] Bounty to sponsor the fix (example)

Description

According to https://swagger.io/docs/specification/describing-parameters/#schema-vs-content we can use content along with a nested schema to specify that query params are encoded as JSON objects. OpenAPIGenerator does not seem to respect this and gives the following error:

Execution failed for task ':openApiGenerate'.
> There were issues with the specification. The option can be disabled via validateSpec (Maven/Gradle) or --skip-validate-spec (CLI).
   | Error count: 1, Warning count: 0
  Errors: 
  	-attribute paths.'/foobar'(get).[jsonFilter].content is unexpected

openapi-generator version

4.3.0 Gradle plugin

OpenAPI declaration file content or url

{"swagger":"3.0.1", "info": {"title": "Content test"}, "host":"localhost","basePath":"/","tags":[{"name":"FooAPI"}],"paths":{"/foobar":{"get":{"tags":["FooAPI"],"operationId":"getFoobar","produces":["application/json"],"parameters":[{"name": "jsonFilter", "in": "query", "type": "object", "content":  {"application/json": {"schema":  {"type": "object", "properties": {"wheeee": "string"}}}}}],"responses":{"200":{"description":"Ok","schema":{"type":"string"}},"400":{"description":"Bad Request","schema":{"type":"string"}}}}}}}

Command line used for generation

openApiGenerate {
    generatorName = "java"
    library = "okhttp-gson"
    inputSpec = "myswagger.yaml"
}

Start by reproducing the validation failure with the provided OpenAPI declaration and the Gradle openApiGenerate configuration using generatorName "java". Trace how query parameters using content are validated, then verify that the same specification passes validation while preserving the expected JSON query-parameter behavior.