Update README.md

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated YOLOv5 inference documentation to simplify and clarify model loading instructions.

📊 Key Changes

• Modified the Inference section in the README to streamline the text.
• Models now explicitly mentioned as downloadable from the latest YOLOv5 release.
• Updated the model loading code example to include a broader range of YOLOv5 models, from 'yolov5n' to 'yolov5x6'.

🎯 Purpose & Impact

• Improved Clarity: The simplification helps users understand the inference process more easily.
• Ease of Use: Automatic download of models from the latest release enhances user convenience.
• Expanded Options: Including a wider array of model names ('yolov5n' - 'yolov5x6') informs users about the available range of model sizes and capabilities. This allows users to make more informed decisions when choosing a model for their specific needs, potentially impacting their applications' performance and efficiency.