[Bug Report] Message content is too long and does not wrap

### Element UI version
2.13.1

### OS/Browsers version
Win10 64/ Chrome 81.0.4044.138（正式版本） （64 位）

### Vue version
2.6.11

### Reproduction Link
https://codepen.io/wxh16144/pen/yLYEKLj

### Steps to reproduce
内容过长不换行
```javascript
this.$message('ABC'.repeat(100));
```
中文换行
```javascript
this.$message('中文'.repeat(100));
```
建议添加css属性 `word-break`

Thanks

### What is Expected?
允许在单词内换行

### What is actually happening?
中文线上正常