속성을 secret.example에 추가해야 함

[Lechros]

https://github.com/ootd-zip/server/blame/9b7c7f164ab4ae2eb9d5c76a86923f923f96f0dc/src/main/java/zip/ootd/ootdzip/images/service/ImagesService.java#L44
cloud.aws.s3.url.prefix이 application-secret.example.yaml에 존재하지 않아요.