[bug report] when v-model.trim is used for El input, spaces cannot be entered between words. Before and after spaces should be removed in the blur event of input

### Element UI version
2.13.1

### OS/Browsers version
window10/80.0.3987.163（正式版本）

### Vue version
3.0.0-alpha.12

### Reproduction Link
https://codepen.io/pen/?&editable=true=https%3A%2F%2Felement.eleme.cn%2F2.13%2F

### Steps to reproduce
1. el-input的v-model添加修饰符.trim
2. 无法输入空格
3.需要先打出文字，再移动光标到文字中间敲空格

### What is Expected?
应该是在输入框blur后去掉前后空格

### What is actually happening?
无法输入空格，要先打出文字后再往中间敲空格