Remove deprecated mappedBy.

pkg/serialization/lib/src/format.dart

Index: pkg/serialization/lib/src/format.dart
diff --git a/pkg/serialization/lib/src/format.dart b/pkg/serialization/lib/src/format.dart
index a1726f0f5b979a82627cc96c356a793509399ba9..36c8042e7af066a4ba183f5732493a9f98837d81 100644
--- a/pkg/serialization/lib/src/format.dart
+++ b/pkg/serialization/lib/src/format.dart
@@ -216,7 +216,7 @@ class SimpleJsonFormat extends Format {
     } else {
       throw new SerializationException("Invalid data format");
     }
-    // Do not use mappedBy or other lazy operations for this. They do not play
+    // Do not use map or other lazy operations for this. They do not play
     // well with a function that destructively modifies its arguments.
     var newData = mapValues(data, (each) => recursivelyFixUp(each, r, result));
     result[ruleNumber].add(newData);