Bug fix: get_code_hash passes str instead of List[str] to get_training_code_has

[Christian-kam]

sagemaker.core.workflow.utilities.get_training_code_hash expects dependencies to be a list, but SourceCode.requirements is passed as a str.

The change wrap requirements in a list before passing it: This ensures dependencies is always a List[str] inside get_training_code_hash, so the [source_dir] + dependencies and [entry_point] + dependencies list concatenations work correctly.

Issue #, if available:
N/A
Description of changes:
Bug Fix: Wrap SourceCode.requirements in a list before passing to get_training_code_hash
get_training_code_hash expects its dependencies parameter to be a List[str], but SourceCode.requirements is a str (a path to a requirements.txt file). When passed directly, the list concatenation [source_dir] + dependencies raises a TypeError:

["my_source_dir"] + "requirements.txt"
TypeError: can only concatenate list (not "str") to list

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Root cause:
In get_code_hash, the TrainingStep branch passes requirements directly:

requirements = source_code.requirements  # str, e.g. "requirements.txt"
return get_training_code_hash(entry_point, source_dir, requirements)

Note that the ProcessingStep branch does not have this issue because it normalizes dependencies into a list via get_processing_dependencies() before passing them.

Fix:
Wrap requirements in a list before passing:

return get_training_code_hash(
    entry_point, source_dir, [requirements] if requirements else []
)

This ensures dependencies is always a List[str] inside get_training_code_hash, so [source_dir] + dependencies and [entry_point] + dependencies work correctly.