Update barback.dart (#2346)

diff --git a/lib/src/command/barback.dart b/lib/src/command/barback.dart
index 442e708..0c34bf2 100644
--- a/lib/src/command/barback.dart
+++ b/lib/src/command/barback.dart
@@ -24,6 +24,6 @@
 
     fail(log.red('Dart 2 has a new build system. Learn how to migrate '
         "from ${log.bold('pub build')} and\n"
-        "${log.bold('pub serve')}: https://webdev.dartlang.org/dart-2\n"));
+        "${log.bold('pub serve')}: https://dart.dev/web/dart-2\n"));
   }
 }