Remove unnecessary import

pkgs/stream_channel/lib/src/json_document_transformer.dart

diff --git a/pkgs/stream_channel/lib/src/json_document_transformer.dart b/pkgs/stream_channel/lib/src/json_document_transformer.dart
index 237193b..3feda43 100644
--- a/pkgs/stream_channel/lib/src/json_document_transformer.dart
+++ b/pkgs/stream_channel/lib/src/json_document_transformer.dart
@@ -7,7 +7,6 @@
 import 'package:async/async.dart';
 
 import '../stream_channel.dart';
-import 'stream_channel_transformer.dart';
 
 /// A [StreamChannelTransformer] that transforms JSON documents—strings that
 /// contain individual objects encoded as JSON—into decoded Dart objects.