DefaultCacheManager emptyCache() do not work

## 🐛 Bug Report

Hi
I'm using DefaultCacheManager to read a file from an URL like bellow :

```
DefaultCacheManager().emptyCache();

file = await DefaultCacheManager()
.getSingleFile(url)
.onError((error, stackTrace) {
isRead = false;
return fil;
});
```

and next time I change file content but first content is returned and emptyCache() do not work .

I tried like below too :

```
DefaultCacheManager dfcm = new DefaultCacheManager();

dfcm.emptyCache();

file = await dfcm
.getSingleFile(url)
.onError((error, stackTrace) {
isRead = false;
return fil;
});
```

### Expected behavior

### Reproduction steps

### Configuration

**Version:** flutter_cache_manager: ^3.3.0

**Platform:**

- [x] :robot: Android