Remove FileTypeRenderer (#2139)

diff --git a/lib/src/render/file_type_renderer.dart b/lib/src/render/file_type_renderer.dart
deleted file mode 100644
index 7f6bbc5..0000000
--- a/lib/src/render/file_type_renderer.dart
+++ /dev/null
@@ -1,12 +0,0 @@
-// Copyright (c) 2020, 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.
-
-abstract class FileTypeRenderer {
-  String get fileType;
-}
-
-class HtmlFileTypeRenderer extends FileTypeRenderer {
-  @override
-  String get fileType => 'html';
-}