fix volume.manageable-volumes schema

another badly constructed schema were squeezing through json and openapi
validation

Change-Id: Ie8f9290a750503332384847fc5d99dbe37b0b322

codegenerator/openapi/cinder_schemas/volume_manage.py

@@ -62,7 +62,7 @@ MANAGEABLE_VOLUME_DETAIL_SCHEMA: dict[str, Any] = {
             "type": ["string", "null"],
             "description": "More information about the resource.",
         },
-        **MANAGEABLE_VOLUME_SCHEMA,
+        **MANAGEABLE_VOLUME_SCHEMA["properties"],
     },
 }