revealjs: Fix update process

[tremor021]

✍️ Description

gulpfile.js we are currently backing up is incompatible with new version. We're not backing it up any more since its a simple sed change anyway.

🔗 Related PR / Issue

Link: #3340

✅ Prerequisites (X in brackets)

• Self-review completed – Code follows project standards.
• Tested thoroughly – Changes work as expected.
• No breaking changes – Existing functionality remains intact.
• No security risks – No hardcoded secrets, unnecessary privilege escalations, or permission issues.

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🛠️ Type of Change (X in brackets)

• 🐞 Bug fix – Resolves an issue without breaking functionality.
• ✨ New feature – Adds new, non-breaking functionality.
• 💥 Breaking change – Alters existing functionality in a way that may require updates.
• 🆕 New script – A fully functional and tested script or script set.
• 🌍 Website update – Changes to website-related JSON files or metadata.
• 🔧 Refactoring / Code Cleanup – Improves readability or maintainability without changing functionality.
• 📝 Documentation update – Changes to README, AppName.md, CONTRIBUTING.md, or other docs.

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🔍 Code & Security Review (X in brackets)

• Follows Code_Audit.md & CONTRIBUTING.md guidelines

📋 Additional Information (optional)