Unable to list notebooks

### **This is autogenerated. Please review and update as needed.**

## Describe the bug
When trying to list notebooks via CLI, I get the error described below. I also have an open Azure support ticket addressing similar behavior in the portal where my notebook went missing and seems to timeout when trying to locate notebooks (just a theory)

**Command Name**
`az synapse notebook list`

**Errors:**
```
Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get'
Traceback (most recent call last):
python3.8/site-packages/msrest/serialization.py, ln 1416, in _deserialize
found_value = key_extractor(attr, attr_desc, data)
python3.8/site-packages/msrest/serialization.py, ln 1160, in rest_key_extractor
return working_data.get(key)
AttributeError: 'str' object has no attribute 'get'

...

python3.8/site-packages/msrest/serialization.py, ln 1160, in rest_key_extractor
return working_data.get(key)
msrest.exceptions.DeserializationError: Unable to deserialize to object: type, AttributeError: 'str' object has no attribute 'get'
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- _Put any pre-requisite steps here..._
`az synapse notebook list --workspace-name {MY_WORKSPACE_NAME}`

## Expected Behavior
I should see a list of notebooks

## Environment Summary
```
macOS-11.2.1-x86_64-i386-64bit
Python 3.8.7
Installer: HOMEBREW

azure-cli 2.17.1 *

Extensions:
databricks 0.7.0
azure-devops 0.18.0

```
## Additional Context

Beginnen Sie am Einstiegspunkt der Liste von az synapse notebook und reproduzieren Sie den Befehl mit einem Workspace-Namen. Vergleichen Sie die zurückgegebenen Notebook-Daten mit dem msrest-Deserialisierungs-Traceback und überprüfen Sie anschließend, dass eine erfolgreiche Ausgabe Notebooks ohne AttributeError auflistet. Die Payload nennt keine Quelldatei und keinen Test, daher erfordert das Auffinden der Implementierung und das Hinzufügen von Abdeckung eine Recherche im Repository.

Vom Indexierungsmodell aus dem Issue-Text verfasst.