[skip ci] Add comment of update result on benchmark (#8921)

Signed-off-by: Nwangting0128 <ting.wang@zilliz.com>

tests/benchmark/milvus_benchmark/metrics/models/metric.py

@@ -51,6 +51,7 @@ class Metric(object):
         self.status = status
 
     def update_result(self, result):
+        # Customized test result update, different test types have different results
         self.metrics["value"].update(result)
 
     def update_message(self, err_message):