[Feature Request] El-upload replace when limit exceeded

### Existing Component
Yes

### Component Name
el-upload

### Description
Hi,

Not sure if this is a feature request, but it's def not a bug. This is my case:

Users should be able to upload only 1 file, but when they choose a new file (so exceed the limit) I want the new file to replace the old one (which is very common with upload fields). However, I cannot seem to get that working. My code:

```


{{ $t('chooseFile') }}

Thank you for helping.