[BUG] `identity` property is missing on the Azure Container App ManagedEnvironment

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/app/resource-manager/Microsoft.App/stable/2024-03-01/ManagedEnvironments.json

### API Spec version

2024-03-01

### Describe the bug

The specification for Azure Container App ManagedEnvironment doesn't contain the `identity` property while it's returned by the actual API. As a result https://github.com/hashicorp/go-azure-sdk doesn't contain this property and https://github.com/hashicorp/terraform-provider-azurerm can't be changed to manage it via Terraform.

### Expected behavior

The specs for the `ManagedEnvironment` contains the `identity` property

### Actual behavior

The `identity` property is missing in the specs for the `ManagedEnvironment`

### Reproduction Steps

Create Azure Container App environment and enable System assigned managed identity. The run:
```
az rest --method get --url https://management.azure.com/subscriptions/xxxx/resourceGroups/xxx-rg/providers/Microsoft.App/managedEnvironments/xxxx-cae?api-version=2024-03-01
```
and find the `identity` in the output

### Environment

_No response_