修复修改题目计数器的时候，多个 save 相互覆盖的 bug

problem/models.py

@@ -50,11 +50,11 @@ class AbstractProblem(models.Model):
 
     def add_submission_number(self):
         self.total_accepted_number += 1
-        self.save()
+        self.save(update_fields=["total_accepted_number"])
 
     def add_ac_number(self):
         self.total_accepted_number += 1
-        self.save()
+        self.save(update_fields=["total_accepted_number"])
 
 
 class Problem(AbstractProblem):