Wrong type hints for optional parameters

[AdrianB-sovo]

Describe the bug
Some optional parameters don't use Union[<type>, None] = None, which is problematic for those that use a type checker.

To reproduce

from typing import List
from sagemaker.workflow.steps import ProcessingStep

def get_job_args() -> List[str] | None
    # In my use-case, the arguments depend on some config, which can be empty.
    return None

process_step = ProcessingStep(
    name="some name",
    job_arguments=get_job_args(), # <- Type checker complains that `List[str] | None` is incompatible with `List[str]`.
)

Expected behavior
The type checker shouldn't give me errors when I use Sagemaker in a valid way.

System information
A description of your system. Please provide:

• SageMaker Python SDK version: 2.215.0
• Python version: 3.11.7

Additional context
I'm using VScode with Pylance configured in strict mode.