表格组件thead的background-clip:padding-box会导致第一个th下面有个空白

[zhangzhi93]

• I have searched the issues of this repository and believe that this is not a duplicate.

Reproduction link

https://github.com/zhangzhi93/movie-admin-project

Steps to reproduce

http://localhost:6060/#/StoreManage/Store

.webpackrc

"theme": {
    "@table-header-bg": "#e0f0ff"
  }

What is expected?

背景颜色填满

What is actually happening?

下面有一个很小的空白

Environment	Info
antd	3.13.4
React	16.8.2
System	windows 10 1709
Browser	chrome 72.0.3626.109