Add torch==1.7.0 to CI tests

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhancement of CI testing to ensure compatibility with older Python and PyTorch versions.

📊 Key Changes

• Added a CI test case for Ubuntu with Python 3.8 and PyTorch 1.7.0.
• Conditional requirements installation based on the specified PyTorch version.
• Moved python --version, pip --version, and pip list commands to a later step in the workflow.

🎯 Purpose & Impact

• Ensures backward compatibility: By testing against older Python and PyTorch versions, Ultralytics ensures that YOLOv5 remains compatible with environments that have not upgraded to the latest versions.
• Reduces potential issues for users: Users on legacy systems will appreciate continued support, minimizing disruption and the need for upgrades.
• Maintains robust testing: By adjusting CI workflows, the project continues to maintain high-quality standards through automated testing.