ModelBuilder import issues in a SageMaker Studio Notebook

## Issue

Hello,

I'm trying to update from SageMaker v2 --> v3, and have had issues with importing the `ModelBuilder` module. I'm trying to follow this documentation: https://github.com/aws/sagemaker-python-sdk/blob/master/v3-examples/ml-ops-examples/v3-pipeline-train-create-registry.ipynb

The error received when importing the `ModelBuilder` module:

```
ModuleNotFoundError: No module named 'sagemaker.serve.spec'
```

## Repro steps

1. Start a SageMaker Studio Jupyter Notebook
2. Install the latest SageMaker v3.1.0 from github directly: `!pip install git+https://github.com/aws/sagemaker-python-sdk.git@v3.1.0`
3. Import the module: `from sagemaker.serve.model_builder import ModelBuilder`

## Screenshot

Start with the v3-examples/ml-ops-examples/v3-pipeline-train-create-registry.ipynb example and reproduce the import in a SageMaker Studio Jupyter Notebook using the reported installation command. Check the `from sagemaker.serve.model_builder import ModelBuilder` entry point and the missing `sagemaker.serve.spec` error; done means the documented import works without ModuleNotFoundError.

Written by the indexing model from the issue text.