use stream_error for both

Author: prwhelan

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/external/openai/OpenAiUnifiedChatCompletionResponseHandler.java

@@ -90,7 +90,7 @@ private static Exception buildMidStreamError(Request request, String message, Ex
                 restStatus,
                 format("%s for request from inference entity id [%s]", SERVER_ERROR_OBJECT, request.getInferenceEntityId()),
                 errorResponse != null ? errorResponse.getClass().getSimpleName() : "unknown",
-                "streaming_error"
+                "stream_error"
             );
         }
     }