Fix checked mode error on socket IOSink

runtime/bin/socket_patch.dart

Index: runtime/bin/socket_patch.dart
diff --git a/runtime/bin/socket_patch.dart b/runtime/bin/socket_patch.dart
index 95e2017b6530626e3e5b49f4f7042f29ccf91509..e697822396c1cfa1b350ed3dc47e915533ecaa98 100644
--- a/runtime/bin/socket_patch.dart
+++ b/runtime/bin/socket_patch.dart
@@ -764,7 +764,10 @@ class _Socket extends Stream<List<int>> implements Socket {
   }
 
   Encoding get encoding => _sink.encoding;
-  void set encoding(Encoding value) => _sink.encoding = value;
+
+  void set encoding(Encoding value) {
+    _sink.encoding = value;
+  }
 
   void write(Object obj) => _sink.write(obj);