Canonical k8s `shared` folder wrong permissions

### Bug Description

Details about the setup can be found in this comment https://github.com/canonical/data-science-stack/issues/187#issuecomment-2604444833

After deploying DSS to Canonical k8s `shared` folder in the notebook is complaining about permissions when trying to create notebook.


### To Reproduce

1. Run steps from this comment https://github.com/canonical/data-science-stack/issues/187#issuecomment-2604444833
2. Create a notebook `data-science-stack.dss create my-notebook-scipy --image=kubeflownotebookswg/jupyter-scipy:v1.8.0`
3. Access the notebook
4. Click on `shared` folder from the left panel
5. Click on Create new notebook

### Environment

Canonical k8s v1.32.0
DSS latest stable (without the microk8s storage class reference)

### Relevant Log Output

```shell
Permission denied: shared/Untitled.ipynb
```

### Additional Context

_No response_