Update artifact boilerplate zip to Python 3.12

[himabindu1410]

This PR refreshes the model artifact boilerplate ZIP so the embedded runtime.yaml matches the Python 3.12 boilerplate files already present in the repository.

Changes:

• Regenerated model_catalog_examples/artifact_boilerplate/artifact_boilerplate.zip
• Updated the ZIP contents to use the Python 3.12 inference conda environment
• Removed stale Python 3.7 references from the ZIP-packaged runtime.yaml

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