nz-table 复杂表头不对其

[liwei511]

Reproduction link

https://stackblitz.com/edit/ng-zorro-antd-start-qb9opj?file=src%2Fapp%2Fapp.component.html

Steps to reproduce

预览窗口，第二行th末端， 列没有对齐

What is expected?

两表头table列对齐

What is actually happening?

两表头table列没有对齐

Environment	Info
ng-zorro-antd	8.1.2
Browser	Chrome/75.0.3770.100

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页面中需要合并单元格的表头

[zorro-bot]

Translation of this issue:

Nz-table complex header does not

Reproduction link

[https://stackblitz.com/edit/ng-zorro-antd-start-qb9opj?file=src%2Fapp%2Fapp.component.html](https://stackblitz.com/edit/ng-zorro-antd- Start-qb9opj?file=src%2Fapp%2Fapp.component.html)

Steps to reproduce

Preview window, the second line is at the end of th, the columns are not aligned

What is expected?

Two table header column alignment

What is actually happening?

Two header table columns are not aligned

Environment	Info
ng-zorro-antd	8.1.2
Browser	Chrome/75.0.3770.100

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The header of the page that needs to merge the cells