#2119. Remove unused code, add issues numbers (#2534)

Author: sgrekhov

LibTest/convert/ChunkedConversionSink/close_A01_t01.test.dart

@@ -20,7 +20,6 @@ test(ChunkedConversionSink create(ChunkedConversionSink<List<int>> outSink)) {
   bool called = false;
   Utf8Codec codec = new Utf8Codec();
   var encoded = codec.encode("Кириллица");
-  Utf8Decoder decoder = new Utf8Decoder();
 
   var outSink = new ChunkedConversionSink<List<int>>.withCallback((accumulated) {
     called = true;

LibTest/typed_data/Float32List/setRange_A06_t01.dart

@@ -13,6 +13,7 @@
 /// @description Checks that it is a run time error if run-time type of the
 /// `iterable` is not subtype of this list. Test data of the same size
 /// @author [email protected]
+/// @issue 53945
 
 import "dart:typed_data";
 import "../../../Utils/expect.dart";

LibTest/typed_data/Float64List/setRange_A06_t01.dart

@@ -13,6 +13,7 @@
 /// @description Checks that it is a run time error if run-time type of the
 /// `iterable` is not subtype of this list. Test list elements of the same size
 /// @author [email protected]
+/// @issue 53945
 
 import "dart:typed_data";
 import "../../../Utils/expect.dart";