fix: add visibility:hidden to selector:after

[kanouken]

在某些情况下，Select会显示字母A；给-selector:after加上了visibility:hidden;样式
如下所示：
.ant-select-multiple .ant-select-selector:after {
content: " ";
display: inline-block;
line-height: 24px;
margin: 2px 0;
width: 0
}