Updates inference test

[picandocodigo]

When updating the endpoint code on the stack client with the elasticsearch-specification, it changes the path of infer_trained_model:

-          path   = ("_ml/trained_models/#{Utils.__listify(_model_id)}/deployment/_infer" if _model_id)
+          path   = "_ml/trained_models/#{Utils.__listify(_model_id)}/_infer"

When using the first path, the response is:
{"predicted_value" => [[1.0, 1.0]]}

But with the updated path, it's returning:
{"inference_results" => [{"predicted_value" => [[1.0, 1.0]]}]}