Tweak message.

pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart

Index: pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
diff --git a/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart b/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
index b88c9233ebfda5a0fcd98043502bf601da6745cb..c3258c0d24bb88148e405e0c22bb3f29be0a468d 100644
--- a/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
+++ b/pkg/front_end/lib/src/fasta/kernel/kernel_class_builder.dart
@@ -230,7 +230,7 @@ abstract class KernelClassBuilder
       addWarning(
           declaredMember.fileOffset,
           "The method '$name::${declaredMember.name.name}' has more "
-          "positional arguments than those of overridden method "
+          "required arguments than those of overridden method "
           "'${interfaceMember.enclosingClass.name}::"
           "${interfaceMember.name.name}'.");
     }