[Bug Report]: EventGrid System Topics can't use private endpoints

[lsnoddy]

Describe the bug

The Microsoft.EventGrid systemTopics module has private endpoint capability built in, however this resource does not support private endpoints. See https://docs.microsoft.com/en-us/azure/private-link/private-endpoint-overview#private-link-resource

Attempting to use private endpoints with the module results in the following error:

To reproduce

1. Add privateEndpoints to the parameters.json
2. Run the pipeline

Code snippet

"privateEndpoints": {
            "value": [
                {
                    "subnetResourceId": "/subscriptions/<<subscriptionId>>/resourceGroups/validation-rg/providers/Microsoft.Network/virtualNetworks/adp-<<namePrefix>>-az-vnet-x-001/subnets/<<namePrefix>>-az-subnet-x-005-privateEndpoints",
                    "service": "topic"
                }
            ]
        },

Relevant log output

No response