fix: available 조건 수정

Author: golony6449

sponsor/serializers.py

@@ -69,4 +69,4 @@ def get_remaining(obj):
 
     @staticmethod
     def get_available(obj: SponsorLevel):
-        return True if obj.current_remaining_number < obj.limit else False
+        return True if obj.current_remaining_number > 0 else False