Add warning emoji ⚠️ on --conf > 0.001

[glenn-jocher]

User error persists despite warnings, adding more visible warning element. Addresses #8004

🛠️ PR Summary

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🌟 Summary

Improvement to validation script messaging with emojis.

📊 Key Changes

• Added emojis function call in the import section of val.py.
• Removed a LOGGER warning about an invalid mAP values due to high confidence threshold.

🎯 Purpose & Impact

• The inclusion of emojis aims to make the script's output more user-friendly and engaging.
• Removing the LOGGER warning about high confidence thresholds cleans up the output and may reduce confusion for users, who can now set higher confidence values without being warned of invalid mAP calculations.