Update ci-testing.yml

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

This PR updates the GitHub Actions workflow for better error notifications via Slack integration in the YOLOv3 project.

📊 Key Changes

• Adjusted the Slack notification settings to use 'incoming-webhook' for error alerts.
• Removed redundant environment variable declaration by directly using the secret in the payload configuration.

🎯 Purpose & Impact

• Enhanced Notification: The change ensures better communication of CI failures to the development team via Slack, allowing for quicker response times. 📢
• Streamlined Configuration: Simplifies the Slack webhook configuration, reducing the potential for errors and improving maintainability. 🛠️

[UltralyticsAssistant]

👋 Hello @glenn-jocher, thank you for submitting an ultralytics/yolov3 🚀 PR! To ensure a seamless integration of your work, please review the following checklist:

• ✅ Define a Purpose: Clearly explain the purpose of your fix or feature in your PR description, and link to any relevant issues. Ensure your commit messages are clear, concise, and adhere to the project's conventions.
• ✅ Synchronize with Source: Confirm your PR is synchronized with the ultralytics/yolov3 main branch. If it's behind, update it by clicking the 'Update branch' button or by running git pull and git merge main locally.
• ✅ Ensure CI Checks Pass: Verify all Ultralytics Continuous Integration (CI) checks are passing. If any checks fail, please address the issues.
• ✅ Update Documentation: Update the relevant documentation for any new or modified features.
• ✅ Add Tests: If applicable, include or update tests to cover your changes and confirm that all tests are passing.
• ✅ Sign the CLA: Please ensure you have signed our Contributor License Agreement if this is your first Ultralytics PR by writing "I have read the CLA Document and I sign the CLA" in a new message.
• ✅ Minimize Changes: Limit your changes to the minimum necessary for your bug fix or feature addition. "It is not daily increase but daily decrease, hack away the unessential. The closer to the source, the less wastage there is." — Bruce Lee

For more guidance, please refer to our Contributing Guide. Don’t hesitate to leave a comment if you have any questions. Thank you for contributing to Ultralytics! 🌟

This is an automated response, but rest assured, an Ultralytics engineer will review your PR soon. 😊