[bug report] when El select is set to filterable, the drop-down box cannot be shrunk

### Element UI version
2.15.6

### OS/Browsers version
windows 10/Chrome 94

### Vue version
2.6.14

### Reproduction Link
https://codepen.io/sharilove/pen/ZEJYxxj

### Steps to reproduce
1.el-select组件设置filterable为true
2.点击下拉箭头，出现下拉框
3.再次点击上箭头，下拉框却不会缩起

### What is Expected?
通过点击箭头展开的下拉框，再次点击箭头可以正常收缩

### What is actually happening?
通过点击箭头展开的下拉框，再次点击箭头却不会缩起