az ml workspace create throws InvalidRequestContent error

### Extension name (the extension in question)

azure-cli-ml

- Using Azure CLI version 2.4.0...
- Using Azure CLI ML extension version 1.3.0...

### Description of issue (in as much detail as possible)

When running [`az ml workspace create --workspace-name anyname -g anyresourcegroup`](https://docs.microsoft.com/en-us/cli/azure/ext/azure-cli-ml/ml/workspace?view=azure-cli-latest#ext-azure-cli-ml-az-ml-workspace-create) I get the following error message:

```
Unable to create the workspace.
Azure Error: InvalidRequestContent
Message: The request content was invalid and could not be deserialized: 'Could not find member 'template' on object of type 'DeploymentDefinition'. Path 'template', line 1, position 12.'.
WorkspaceException:
Message: Unable to create the workspace. The request content was invalid and could not be deserialized: 'Could not find member 'template' on object of type 'DeploymentDefinition'. Path 'template', line 1, position 12.'.
InnerException Azure Error: InvalidRequestContent
Message: The request content was invalid and could not be deserialized: 'Could not find member 'template' on object of type 'DeploymentDefinition'. Path 'template', line 1, position 12.'.
ErrorResponse
{
"error": {
"message": "Unable to create the workspace. The request content was invalid and could not be deserialized: 'Could not find member 'template' on object of type 'DeploymentDefinition'. Path 'template', line 1, position 12.'."
}
}
```

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