Update format.yml to pull_request_target

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Updated GitHub Actions workflow to enhance PR handling and formatting checks.

📊 Key Changes

• Changed the trigger event from pull_request to pull_request_target for formatting workflow.

🎯 Purpose & Impact

• Enhanced Security: The pull_request_target event allows workflows to run with a higher level of security when interacting with pull requests from forks.
• Improved PR Handling: Ensures that the correct base branch is used in the formatting checks, improving accuracy and reliability.

This update optimizes the workflow handling for pull requests, enhancing both security and efficiency when managing incoming contributions. 🚀🔒