Remove unsupported S3 artifact reference placeholder

internal/artifact/reader_test.go

@@ -46,7 +46,7 @@ func TestCompositeReader_Read(t *testing.T) {
 
 	t.Run("unsupported ref type", func(t *testing.T) {
 		ref := domain.ArtifactRef{
-			Type: domain.ArtifactRefS3,
+			Type: domain.ArtifactRefType("s3"),
 			URI:  "s3://bucket/key",
 		}
 		_, err := reader.Read(ctx, ref)

internal/domain/domain.go

@@ -10,7 +10,6 @@ type ArtifactRefType string
 const (
 	ArtifactRefInline ArtifactRefType = "inline"
 	ArtifactRefFile   ArtifactRefType = "file"
-	ArtifactRefS3     ArtifactRefType = "s3"
 )
 
 // OutputFormat defines the desired format of the generated artifact.