Fix doc comment.

sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart

Index: sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
diff --git a/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart b/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
index 5418b9173787d5c9dc0cf0375bafffe3b47bb516..1c2c38b676cd4d597c5abce9ee3f3229e87dfeaa 100644
--- a/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
+++ b/sdk/lib/_internal/pub/lib/src/barback/load_all_transformers.dart
@@ -21,7 +21,7 @@ import '../utils.dart';
 /// loaded, then adds the transformers to `server.barback`.
 ///
 /// Any [builtInTransformers] that are provided will automatically be added to
-/// the end of every package's cascade.
+/// the end of the root package's cascade.
 Future loadAllTransformers(BarbackServer server, PackageGraph graph,
     BarbackMode mode, Iterable<Transformer> builtInTransformers) {
   // In order to determine in what order we should load transformers, we need to