samples(dart): tweak template-syntax sample

closes #1130

public/docs/_examples/template-syntax/dart/lib/app_component.html

@@ -259,7 +259,8 @@ Property bound: <img [src]="heroImageUrl">
 <!-- reset/override all class names with a binding  -->
 <div class="bad curly special"
      [class]="badCurly">Bad curly</div>
-     <!-- Doesn't work, due to github.com/angular/angular/issues/6901 -->
+<p><b>Note:</b> "Bad curly" should be smaller but isn't, due to
+  <a href="http://github.com/angular/angular/issues/6901">issue #6901</a>.</p>
 <!-- #enddocregion class-binding-2 -->
 
 <!-- #docregion class-binding-3 -->