fix(sct_runner): change disk type for image creation

we don't need the `Premium_LRS` managed disks for creation
of the SCT runner

it was failing with the following error:
```
azure.core.exceptions.HttpResponseError: (InvalidParameter) Requested operation cannot
be performed because the VM size Standard_D2_v4 does not support the storage account type
Premium_LRS of disk 'sct-runner-1.7-builder-eastus'. Consider updating the VM to a size
that supports Premium storage.

Code: InvalidParameter

Message: Requested operation cannot be performed because the VM size Standard_D2_v4
does not support the storage account type Premium_LRS of disk 'sct-runner-1.7-builder-eastus'.
Consider updating the VM to a size that supports Premium storage.

Target: osDisk.managedDisk.storageAccountType
```

sdcm/utils/azure_region.py

@@ -318,7 +318,7 @@ def create_virtual_machine(self,  # pylint: disable=too-many-arguments
                         "caching": "ReadWrite",
                         "create_option": "FromImage",
                         "managed_disk": {
-                            "storage_account_type": "Premium_LRS",  # SSD
+                            "storage_account_type": "StandardSSD_LRS",  # SSD
                         },
                     } | ({} if disk_size is None else {
                         "disk_size_gb": disk_size,