ModelDataUrl is incorrect when result_path is defined in TrainingStep

The ModelDataUrl in the Step Functions' defenition is '“ModelDataUrl.$“: “$[‘ModelArtifacts’][‘S3ModelArtifacts’]”' even though the result_path is defined in the TrainingStep, and it causes error like this.

> “An error occurred while executing the state ‘Save Model’ (entered at the event id #8). The JSONPath ’$[‘ModelArtifacts’][‘S3ModelArtifacts’]' specified for the field ‘ModelDataUrl.$’ could not be found in the input ...

It should be '“ModelDataUrl.$“: “$[‘TrainingStepResults’][‘ModelArtifacts’][‘S3ModelArtifacts’]”'.

```
training_step = steps.TrainingStep(
‘Model Training’,
estimator=tf_estimator,
data={
‘training’: inputs
},
job_name=execution_input[‘TrainingJobName’],
result_path=‘$.TrainingStepResults’,
wait_for_completion=True
)

model_step = steps.ModelStep(
‘Save Model’,
model=training_step.get_expected_model(),
model_name=execution_input[‘ModelName’],
instance_type=‘ml.m5.xlarge’,
result_path=‘$.ModelStepResults’
)
```

从构建 Step Functions 定义的 TrainingStep 和 ModelStep 定义开始，然后跟踪 result_path 如何应用于 ModelDataUrl。复现提供的 training_step 和 model_step 配置，并验证生成的路径嵌套在 TrainingStepResults 下，同时模型输出仍然可用。

由索引模型根据 Issue 内容生成。