`ModelTrainer` bug with method to load hyperparameters from file for Amazon Nova Recipe

[admivsn]

**PySDK Version**

• PySDK V2 (2.x)
• [x ] PySDK V3 (3.x)

Describe the bug
Code is using method self._validate_and_load_hyperparameters_file instead of self._validate_and_fetch_hyperparameters_file`:

        if is_nova:
            if hyperparameters and isinstance(hyperparameters, str):
                hyperparameters = cls._validate_and_load_hyperparameters_file(hyperparameters) # bug
                model_trainer_args["hyperparameters"].update(hyperparameters)
            elif hyperparameters and isinstance(hyperparameters, dict):
                model_trainer_args["hyperparameters"].update(hyperparameters)

To reproduce

from sagemaker.train.model_trainer import ModelTrainer
from sagemaker.train.configs import Compute

model_trainer = ModelTrainer.from_recipe(
    training_image="327873000638.dkr.ecr.us-east-1.amazonaws.com/hyperpod-recipes:verl-v1.0.0-smtj",
    training_recipe="training/nova/nova_1_0/nova_lite/CPT/nova_lite_1_0_p5x16_gpu_pretrain",
    compute=Compute(instance_type="ml.m5.xlarge"),
    hyperparameters="test",
)

│                                                                                                  │
│   287 │   │   │   private_attributes = self.__dict__.get('__private_attributes__')               │
│   288 │   │   │   if private_attributes and item in private_attributes:                          │
│   289 │   │   │   │   return private_attributes[item]                                            │
│ ❱ 290 │   │   │   raise AttributeError(item)                                                     │
│   291 │                                                                                          │
│   292 │   @classmethod                                                                           │
│   293 │   def __prepare__(cls, *args: Any, **kwargs: Any) -> dict[str, object]:                  │
╰──────────────────────────────────────────────────────────────────────────────────────────────────╯
AttributeError: _validate_and_load_hyperparameters_file

Expected behavior
No AttributeError to be raised when using hyperparameter file (string).