nixos/outline: Remove references to minio (#494633)

        To support uploading of images for avatars and document attachments an

        s3-compatible storage can be provided. AWS S3 is recommended for

        redundancy however if you want to keep all file storage local an

        alternative such as [minio](https://github.com/minio/minio)

        alternative such as [garage](https://garagehq.deuxfleurs.fr/)

        can be used.

        Local filesystem storage can also be used.

        {

          accessKey = "...";

          secretKeyFile = "/somewhere";

          uploadBucketUrl = "https://minio.example.com";

          uploadBucketUrl = "https://garage.example.com";

          uploadBucketName = "outline";

          region = "us-east-1";

        }