[Bug] name your bug an unexpected keyword argument 'stft_backend'

- [ ] I didn't find a similar issue already open.
- [x] I read the documentation (README AND Wiki)
- [x] I have installed FFMpeg
- [x] My problem is related to Spleeter only, not a derivative product (such as Webapplication, or GUI provided by others)

## Description

## Step to reproduce

1. Installed using `...`
2. Run as `...`
3. Got `...` error

## Output

```bash
Share what your terminal says when you run the script (as well as what you would expect).
```

## Environment

| | |
| ----------------- | ------------------------------- |
| OS | Windows / Linux / MacOS / other |
| Installation type | Conda / pip / other |
| RAM available | XGo |
| Hardware spec | GPU / CPU / etc ... |

## Additional context