Migrate ordinary I/O from confined file helpers

internal/artifacts/prepared_input_test.go

@@ -130,22 +130,6 @@ func TestResolvePreparedInputRejectsInvalidCanonicalFile(t *testing.T) {
 			},
 			wantErr: "open prepared input source",
 		},
-		{
-			name: "symlink",
-			mutate: func(t *testing.T, path string) {
-				outside := filepath.Join(t.TempDir(), "outside.json")
-				if err := os.WriteFile(outside, []byte("outside\n"), 0o644); err != nil {
-					t.Fatalf("WriteFile(outside) error = %v", err)
-				}
-				if err := os.Remove(path); err != nil {
-					t.Fatalf("Remove() error = %v", err)
-				}
-				if err := os.Symlink(outside, path); err != nil {
-					t.Fatalf("Symlink() error = %v", err)
-				}
-			},
-			wantErr: "not a regular file",
-		},
 		{
 			name: "directory",
 			mutate: func(t *testing.T, path string) {