[Bug Report] component open in codepen can not display in correct style

### Element UI version
2.15.7

### OS/Browsers version
chrome@102.0.5005.61

### Vue version
2.7.0-alpha.4

### Reproduction Link
https://codepen.io/pen?editors=1111

### Steps to reproduce
1、打开官网，找到组件菜单
2、选择Dropdown 下拉菜单
3、查看基础用法中的在线运行
4、打开codepen，组件样式错乱

### What is Expected?
display component style correct

### What is actually happening?
Disordered component style