[Bug Report] input文本域自适应文本高度，【bug】在文字行数多的时候出现滚动条

### Element UI version
2.15.9

### OS/Browsers version
72

### Vue version
2.7.5

### Reproduction Link
https://elementui.github.io/issue-generator

### Steps to reproduce
https://element.eleme.cn/#/zh-CN/component/input#autocomplete-methods
线上版本可复现

### What is Expected?
预期不出现滚动条

### What is actually happening?
结果出现滚动条