Unable to create System Topic for PolicyInsights

## Describe the bug

**Command Name**
`az eventgrid system-topic create`

**Errors:**
```
The requested operation on resource 'Microsoft.EventGrid/systemTopics/azure-policy-events' failed since identity is unavailable for location 'global'. Resource identity is supported in the following locations 'southafricanorth, southafricawest, uaenorth, australiacentral, australiaeast, australiasoutheast, canadacentral, canadaeast, brazilsouth, centralindia, westindia, southindia, japanwest, japaneast, eastasia, southeastasia, koreacentral, koreasouth, northeurope, westeurope, ukwest, uksouth, switzerlandnorth, germanywestcentral, centralus, northcentralus, eastus, eastus2, southcentralus, westus, westus2, westus3, westcentralus, francecentral, norwayeast'.
```

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

- az eventgrid system-topic create --name azure-policy-events --location global --topic-type Microsoft.PolicyInsights.PolicyStates --source "/subscriptions/xxxx" --resource-group "rg-xxxx"

## Expected Behavior
System topic should be created

## Environment Summary
```
Linux-5.10.25-linuxkit-x86_64-with-glibc2.29
Python 3.8.5
Installer: PIP

azure-cli 2.22.1 *

Extensions:
account 0.2.1

```
## Additional Context