[bug report] Select drop-down box component, the drop-down box cannot be retracted

### Element UI version
2.15.0

### OS/Browsers version
windows10/goole

### Vue version
2.6.12

### Reproduction Link
https://github.com/ElemeFE/element/blob/dev/FAQ.md#%E5%B8%B8%E8%A7%81%E9%97%AE%E9%A2%98

### Steps to reproduce
API网站select 可搜索框，点击下拉图标下拉之后再次点击无法收回

### What is Expected?
点击下拉图标下拉框可收回

### What is actually happening?
当前无法收回