[Bug Report] when textarea in form and textarea show-word-limit,it's not in the right style

### Element UI version
2.14.1

### OS/Browsers version
chrome

### Vue version
2.6.12

### Reproduction Link
https://codepen.io/vgbire/pen/zYKWyJY

### Steps to reproduce
textarea set show-word-limit,put it on the form label

### What is Expected?
.el-input__count line-height will Inherit .el-form-item__content line-height cause style confusion, we should We should give it an line-height attribute

### What is actually happening?
.el-input__count line-height style is inherited, the style is disordered