[BUG] The `Identity` block is referenced with wrong type

### API Spec link

https://github.com/Azure/azure-rest-api-specs/blob/main/specification/paloaltonetworks/resource-manager/PaloAltoNetworks.Cloudngfw/stable/2025-05-23/PaloAltoNetworks.Cloudngfw.json#L5400C1-L5403C11

### API Spec version

2025-05-23, 2025-10-08

### Describe the bug

The identity block [only supports](https://learn.microsoft.com/en-us/rest/api/cloudngfw/firewalls/create-or-update?view=rest-cloudngfw-2025-05-23&tabs=HTTP#azure.resourcemanager.managedidentityproperties) `UserAssignedIdentity`. But it's defined as [ManagedServiceIdentity](https://github.com/Azure/azure-rest-api-specs/blob/main/specification/paloaltonetworks/resource-manager/PaloAltoNetworks.Cloudngfw/stable/2025-05-23/PaloAltoNetworks.Cloudngfw.json#L5400C1-L5403C11), which accepts `SystemAssigned`, `UserAssignedIdentity` and `SystemAssigned, UserAssignedIdentity`. The consequence is that downstream SDKs will match a wrong type for this property and causing confusions during development.

Relevant with https://github.com/Azure/azure-rest-api-specs/issues/22634

### Expected behavior

Correct type should be used for the identity block.

For example: https://github.com/Azure/azure-rest-api-specs/blob/main/specification/cosmos-db/resource-manager/Microsoft.DocumentDB/stable/2022-05-15/managedCassandra.json#L771
https://github.com/Azure/azure-rest-api-specs/blob/main/specification/network/resource-manager/Microsoft.Network/stable/2022-07-01/firewallPolicy.json#L955

### Actual behavior

Wrong type is used for `Identity`

### Reproduction Steps

As indicated in Microsoft learn and Swagger above

### Environment

_No response_

Open specification/paloaltonetworks/resource-manager/PaloAltoNetworks.Cloudngfw/stable/2025-05-23/PaloAltoNetworks.Cloudngfw.json around lines 5400-5403 and review the linked API documentation. Compare the identity definitions in the referenced Cosmos DB and Network examples. Done means the Identity block uses a type that supports only UserAssignedIdentity, with the specification validating successfully.

Written by the indexing model from the issue text.