Update onnx>=1.12.0

[glenn-jocher]

https://onnxruntime.ai/docs/reference/compatibility.html

🛠️ PR Summary

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🌟 Summary

Adjustment to ONNX export requirements to ensure compatibility and stability.

📊 Key Changes

• Updated the minimum required version of ONNX for exporting models to 1.12.0 in export.py.
• Modified requirements.txt to reflect the new minimum ONNX version requirement.

🎯 Purpose & Impact

• 🎯 Purpose: To ensure that model export to ONNX format is stable and takes advantage of the latest features and fixes that come with ONNX 1.12.0.
• 🎯 Impact: Users will need to update their ONNX package to at least version 1.12.0 to export their models. This could lead to improved export performance and fewer export-related issues.