The header is misalignment in safari browser use “Header Grouping With Columns Fixed ”

### I am opening an issue for
vue-easytable

### Issue Type
Bug

### Issue Title
“Header Grouping With Columns Fixed ” The header is misalignment in safari browser
“表头分组结合固定列” Safari中表头错位

### library Version
v2.14.0

### Vue Type
2.6.11

### Browser Type
macOS 12.2.1 Safari Version 15.3 (17612.4.9.1.8)

### System version
macOS 12.2.1 iOS 15.3.1

### Reproduction url
https://happy-coding-clans.github.io/vue-easytable/#/zh/doc/table/header-grouping?anchor=biao-tou-fen-zu-jie-he-gu-ding-lie

### Step to reproduce
Open the 2.14.3 version of the official website example of "Header Grouping Combined with Fixed Columns" in Safari. Scrolling up and down will cause the column misalignment problem with multiple rows in the header.

用Safari 打开 2.14.3 版本的 “表头分组结合固定列 ”官网示例，上下滚动行会出现表头中包含多行的列错位问题。

### What is expected?
The header displayed correctly

### What is actually happening?