Fix publish.yml

[glenn-jocher]

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🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhancements to the Python environment setup and version checking in the publish workflow for a MkDocs plugin.

📊 Key Changes

• 🔣 Uncomments and sets the Python version to 3.11 for the workflow environment.
• 🔄 Simplifies version extraction from pyproject.toml with improved variable naming.
• ✨ Switches from shell echo commands to Python's os.system calls for environment variable setting.

🎯 Purpose & Impact

• 🐍 Ensures compatibility with Python 3.11, potentially improving performance and leveraging new language features.
• 🧹 Code cleanup for better readability and maintainability in the version check logic.
• 📈 More robust environment variable setting within the GitHub Action, which could prevent potential bugs and streamline the CI/CD process.
• 📦 Users can expect more reliable updates and packaging for the MkDocs plugin, enhancing the documentation experience.