[bug report] when the table scrolls horizontally or up and down, the header or column will shake, so the experience is very bad

### Element UI version
2.15.1

### OS/Browsers version
mac/ chrome 90.0.4430.85（正式版本)

### Vue version
2.6.11

### Reproduction Link
https://codepen.io/itsmisa/pen/YzNggPe

### Steps to reproduce
table内容超出固定高度或者宽度，上下或者左右滚动的时候，会出现抖动

### What is Expected?
期望上下或者左右滚动的时候，table不抖动

### What is actually happening?
上下或者左右滚动的时候，table会抖动