Microsoft.Web/serverfarms: skuCapacity should be read-only

### Resource Type

Microsoft.Web/serverfarms

### Api Version

2022-09-01

### Issue Type

Property(s) should be marked as read-only/write-only

### Other Notes

{"code": "InvalidTemplate", "target": "/subscriptions/tenantid/resourceGroups/my-rg/providers/Microsoft.Resources/deployments/my-deployment", "message": "Deployment template parse failed: 'Could not find member 'skuCapacity' on object of type 'ResourceSku'. Path 'skuCapacity', line 1, position 5617.'."}

### Bicep Repro

```
resource appServicePlan 'Microsoft.Web/serverfarms@2022-09-01' = {
name: appServicePlanName
location: location
sku: {
skuCapacity: {
default: 1
}
}
}
```

### Confirm

- [X] I have read the troubleshooting guide and looked for duplicates.

Start by locating the Microsoft.Web/serverfarms definition for API version 2022-09-01 and inspect the skuCapacity property against the supplied Bicep repro. Confirm the intended read-only behavior and validate the definition with the deployment scenario; done means the type metadata matches the service contract and the reported template parse error is addressed.

Written by the indexing model from the issue text.