Update PULL_REQUEST_TEMPLATE.md

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhancing the clarity in the Pull Request (PR) template regarding the Contributor License Agreement (CLA) signing statement.

📊 Key Changes

• Modified the CLA signing statement to be more direct and clear by changing "I hereby sign the CLA" to "I sign the CLA".

🎯 Purpose & Impact

• Simplify Communication: This tweak makes the language simpler and more to the point, potentially reducing confusion for contributors about how to express their agreement to the CLA.
• Streamline Process: By having clearer language, the process of signing the CLA is streamlined, leading to a smoother contribution process for new developers.
• Broader Understanding: Ensures both technical and non-technical contributors understand the commitment they are making by signing the CLA, thus maintaining project integrity and quality.

Overall, this minor but impactful change fosters a more inclusive and efficient contributing environment for everyone involved with the Ultralytics projects 🚀.