fixed error (dict access in python is dict["key"])

logscoremetric.py

@@ -145,5 +145,5 @@ class LogScoreMetric(evaluate.Metric):
 
         return {
             "timestamp_score": timestamp_score,
-            "sacrebleu_score": sb_results.score,
+            "sacrebleu_score": sb_results["score"],
         }