Identity cannot be set to type None on Microsoft.Automation/automationAccounts

Hi
I have tried several different versions of the API but you cannot set the identity to type None when using ARM Template. When you set it to None and when you run the template deployment some error like automation account does not exists is returned and the general error is Bad request. The API works fine if it type is SystemAssigned, UserAssigned or SystemAssigned or UserAssigned

```
{
"name": "[parameters( 'automationAccount' ).name]",
"type": "Microsoft.Automation/automationAccounts",
"apiVersion": "2021-06-22",
"location": "[resourceGroup().location]",
"tags": "[parameters( 'tags' )]",
"identity": {
"type": "None"
}
```

Start by locating the Microsoft.Automation/automationAccounts specification for apiVersion 2021-06-22 and tracing how the identity type is modeled. Reproduce the ARM Template deployment with identity.type set to None, compare it with the working identity values, and consider the issue complete when the None deployment succeeds without the misleading missing-account or Bad Request error.

Written by the indexing model from the issue text.