remove docgen source and targets from build

pkg/docgen/lib/src/models.dart

Index: pkg/docgen/lib/src/models.dart
diff --git a/pkg/docgen/lib/src/models.dart b/pkg/docgen/lib/src/models.dart
deleted file mode 100644
index ad61145741b388856c85c8eb42c54a794eefca1f..0000000000000000000000000000000000000000
--- a/pkg/docgen/lib/src/models.dart
+++ /dev/null
@@ -1,13 +0,0 @@
-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-library docgen.models;
-
-export 'models/class.dart';
-export 'models/indexable.dart';
-export 'models/library.dart';
-export 'models/method.dart';
-export 'models/parameter.dart';
-export 'models/typedef.dart';
-export 'models/variable.dart';