Update cla.yml

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced GitHub workflow permissions and updated branch handling in the CLA setup.

📊 Key Changes

• Permissions Update: Added write permissions for actions, contents, pull-requests, and statuses.
• Branch Handling: Changed the branch for storing CLA signatures from “main” to “cla-signatures”.

🎯 Purpose & Impact

• Improved Workflow Automation: With the updated permissions, the workflow can now manage actions, content, and pull requests more effectively, ensuring smoother operations. 🛠️
• Better Organization: Storing CLA signatures in a dedicated branch (cla-signatures) helps in keeping the main branch clean and organized. 📂