Update on_train_end callback

[glenn-jocher]

🛠️ PR Summary

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🌟 Summary

Streamlining result logging in YOLOv5's training script.

📊 Key Changes

• Removed a line in train.py that reported saving results to a directory.
• Added similar logging functionality in utils/loggers/__init__.py, ensuring that results are logged through the logger object.

🎯 Purpose & Impact

• The adjustment ensures that all logging goes through the designated logger, maintaining consistency and potentially making it easier to control output from a single point.
• This change has a minor impact on users: anyone reviewing the training output will now receive a slightly neater log message.
• It simplifies the codebase by removing redundant lines, thus helping contributors with clearer code to maintain.

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