refactor(useInViewport): remove intersection-observer polyfill

[guoyunhe]

[中文版模板 / Chinese template]

🤔 This is a ...

• [ ] New feature
• [ ] Bug fix
• [ ] Site / documentation update
• [ ] Demo update
• [ ] TypeScript definition update
• [x] Bundle size optimization
• [ ] Performance optimization
• [ ] Enhancement feature
• [ ] Internationalization
• [ ] Refactoring
• [ ] Code style optimization
• [ ] Test Case
• [ ] Branch merge
• [ ] Other (about what?)

🔗 Related issue link

💡 Background and solution

根据 caniuse，Chrome 51+ 都支持 IntersectionObserver，不需要 polyfill。

📝 Changelog

Language	Changelog
🇺🇸 English
🇨🇳 Chinese

☑️ Self Check before Merge

⚠️ Please check all items below before review. ⚠️

• [ ] Doc is updated/provided or not needed
• [ ] Demo is updated/provided or not needed
• [ ] TypeScript definition is updated/provided or not needed
• [ ] Changelog is provided or not needed