Update cla.yml

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated CLA workflow to enhance contributor agreement processes.

📊 Key Changes

• 🔒 Added permissions settings for actions, contents, pull-requests, and statuses.
• 🆙 Upgraded the CLA Assistant GitHub Action from version 2.3.2 to 2.4.0.
• 📝 Modified branch from "main" to "cla-signatures" for storing CLA signatures.

🎯 Purpose & Impact

• 🔧 Improved Automation: Enhanced automation for managing Contributor License Agreements (CLAs).
• 🔒 Secured Permissions: By specifying permissions, it ensures better security for handling GitHub Actions.
• 🆙 Latest Features: Using the latest version of CLA Assistant ensures more reliable and up-to-date operations.
• 📄 Organized CLA Signatures: Storing signatures in a dedicated branch ("cla-signatures") for better organization and management.

These changes streamline contributor agreement processes, making it smoother for new contributors to sign the CLA and ensuring overall better project management.