Remove redundant speed/study half argument

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Streamlined benchmark and study test arguments in YOLOv5 test.py.

📊 Key Changes

• Removed the half parameter from test function calls within 'speed' and 'study' tasks.
• Simplified the function call by omitting an explicit argument for mixed precision testing.

🎯 Purpose & Impact

• Simplification: Removing the half parameter simplifies the code and could potentially centralize mixed precision handling within the test function itself.
• Consistency: Ensures consistent function calls across different testing scenarios.
• Performance: This change may impact how the model runs during testing scenarios, particularly how it handles mixed precision for speed benchmarks and study tasks.