Fix some bad documentation links.

sdk/lib/core/invocation.dart

Index: sdk/lib/core/invocation.dart
diff --git a/sdk/lib/core/invocation.dart b/sdk/lib/core/invocation.dart
index 27418417484ab686c678c1399d167afd73225d87..c5f8921ffd00df900e81a9b34f8c1465c38cb218 100644
--- a/sdk/lib/core/invocation.dart
+++ b/sdk/lib/core/invocation.dart
@@ -42,7 +42,7 @@ abstract class Invocation {
   /**
    * Whether the invocation was a setter call.
    *
-   * If so, [arguments] has exactly one positional argument,
+   * If so, [positionalArguments] has exactly one positional argument,
    * and [namedArguments] is empty.
    */
   bool get isSetter;