[bug report] when the check box is disabled, the mouse pattern displayed when the mouse hovers at the edge of the check box should not be a pointer

### Element UI version
2.13.1

### OS/Browsers version
所有版本

### Vue version
2.6.11

### Reproduction Link
https://codepen.io/wztscau/pen/QWjZNVb

### Steps to reproduce
1、使用一个disabled的checkbox
2、悬浮在复选框边缘
3、鼠标 cursor 从 not-allowed 突然变成 pointer

### What is Expected?
1、整个disabled 的 checkbox 都应该是cursor: pointer 状态

### What is actually happening?
在复选框边缘位置 cursor 突然变成pointer