[observe] use consistent comment style

pkg/observe/lib/src/list_path_observer.dart

Index: pkg/observe/lib/src/list_path_observer.dart
diff --git a/pkg/observe/lib/src/list_path_observer.dart b/pkg/observe/lib/src/list_path_observer.dart
index 5c7f1be21b26d0553682f5a301b1d78501e8266d..44b2759d47f427e362e57e8539d76235be49aae9 100644
--- a/pkg/observe/lib/src/list_path_observer.dart
+++ b/pkg/observe/lib/src/list_path_observer.dart
@@ -11,9 +11,7 @@ import 'package:observe/observe.dart';
 // https://raw.github.com/rafaelw/ChangeSummary/master/util/array_reduction.js
 // The main difference is we support anything on the rich Dart Iterable API.
 
-/**
- * Observes a path starting from each item in the list.
- */
+/// Observes a path starting from each item in the list.
 class ListPathObserver<E, P> extends ChangeNotifier {
   final ObservableList<E> list;
   final String _itemPath;