Fix hashicorp/terraform-provider-google#18085

mmv1/products/identityplatform/Config.yaml

@@ -233,6 +233,7 @@ properties:
     name: 'smsRegionConfig'
     description: |
       Configures the regions where users are allowed to send verification SMS for the project or tenant. This is based on the calling code of the destination phone number.
+    default_from_api: true
     properties:
       - !ruby/object:Api::Type::NestedObject
         name: 'allowByDefault'