Update action.yml with PR summary fix

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced the triggering conditions for PR Summarization.

📊 Key Changes

• Renamed the summarization step from "Summarize PR" to "PR Summary" for clarity.
• Modified the conditional check to trigger summarization from inputs.event.action to github.event.action.

🎯 Purpose & Impact

• These changes aim to ensure the summarization step is more intuitively named and correctly triggered according to the pull request's lifecycle events (opened or closed).
• The change could lead to a more reliable workflow execution, providing users with clearer and timely summaries triggered accurately in response to pull request events. 🛠️ ➡️ 📋