[Bug] syntax error in linked Colab notebook

- [x] 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

One of the cells in the linked Colab notebook causes a syntax error.

## Step to reproduce

1. Go to the linked Colab notebook at https://colab.research.google.com/github/deezer/spleeter/blob/master/spleeter.ipynb
2. Run all cells
3. In cell 12, the code `!spleeter separate -h` causes an error.

## Output

```bash
Usage: spleeter separate [OPTIONS] FILES...
Try 'spleeter separate --help' for help.

Error: no such option: -h
```