table: when header is fixed, header scrollbar should not be displayed

[abenhamdine]

Version

3.0.0RC4

Environment

Windows 10, Chrome 63

Reproduction link

http://beta.ant.design/components/table/#components-table-demo-fixed-header

Steps to reproduce

Just see header in example http://beta.ant.design/components/table/#components-table-demo-fixed-header

What is expected?

If the header is fixed, no scrollbar should be displayed for the header

What is actually happening?

The vertical scrollbar is displayed, while useless because disabled

---

Possible fix:

.ant-table-fixed-header .ant-table-scroll .ant-table-header {
    overflow: hidden; /* instead of overflow:scroll */
}

[afc163]

#6800