[Bug] Bump Librosa Version

## Description

Hi, can we please bump the librosa version?

## Step to reproduce

Try to use a new version of librosa and spleeter packages in the same project.

For example: `pip install spleeter librosa==0.10.0.post2`

## Output

See this error related to spleeter locking in old versions of librosa.
```
The conflict is caused by:
The user requested librosa==0.10.0.post2
spleeter 2.3.2 depends on librosa<0.9.0 and >=0.8.0
The user requested librosa==0.10.0.post2
spleeter 2.1.0 depends on librosa==0.8.0
```

## Environment

| | |
| ----------------- | ------------------------------- |
| OS | MacOS |
| Installation type | pip |
| Hardware spec | CPU |

## Additional context

I would update the requirements.txt file and make sure the tests are passing, but I didn't see a requirements.txt file or mention of the librosa package in the source code, so wasn't quite sure about how to proceed. Happy to update if you are able to provide some guidance.

Thanks!