Merge pull request #36 from pers0n4/hotfix/user-model-str-method

`Sponsor` 모델 `__str__` 메서드 오타 수정

Author: golony6449

sponsor/models.py

@@ -150,5 +150,5 @@ class Meta:
     created_at = models.DateTimeField(auto_now_add=True)
     updated_at = models.DateTimeField(auto_now=True)
 
-    def __str_(self):
+    def __str__(self):
         return f"{self.name}/{self.level}"