cleanup patch generation to preseve comments and remove @patch

test/dart_codegen/expect/convert/utf.dart

Index: test/dart_codegen/expect/convert/utf.dart
diff --git a/test/dart_codegen/expect/convert/utf.dart b/test/dart_codegen/expect/convert/utf.dart
index a63d74456be7eb7abaf68c724637e1706577a167..222589a8e0babba49c67520191392c7cc8075d2c 100644
--- a/test/dart_codegen/expect/convert/utf.dart
+++ b/test/dart_codegen/expect/convert/utf.dart
@@ -183,7 +183,7 @@ class Utf8Decoder extends Converter<List<int>, String> {
       DDC$RT.type((DDC$async$.Stream<String> _) {}), "CastDynamic",
       """line 361, column 52 of dart:convert/utf.dart: """,
       __x31 is DDC$async$.Stream<String>, false))(super.bind(stream));
-  @patch Converter<List<int>, dynamic> fuse(Converter<String, dynamic> next) {
+  Converter<List<int>, dynamic> fuse(Converter<String, dynamic> next) {
     return super.fuse(next);
   }
 }