Remove unused simple_accuracy_metric

lm_eval/tasks/common.py

 import datasets
-import lm_eval.metrics
 from ..base import Task
 
 
@@ -43,15 +42,6 @@ class HFTask(Task):
             return self.data["test"]
 
 
-def simple_accuracy_metric(preds, golds):
-    acc = float(lm_eval.metrics.mean())
-    return {
-        "major": acc,
-        "minor": {"acc": acc},
-        "higher_is_better": True,
-    }
-
-
 def yesno(x):
     if x:
         return 'yes'