docs(guide/directive): fix broken link

Fix broken internal link in directive documentation.

Closes angular#6802

docs/content/guide/directive.ngdoc

@@ -510,7 +510,7 @@ that you explicitly pass in.
 
 <div class="alert alert-warning">
 **Note:** Normally, a scope prototypically inherits from its parent. An isolated scope does not.
-See the {@link guide/directive#creating-custom-directives_demo_isolating-the-scope-of-a-directive
+See the {@link guide/directive#isolating-the-scope-of-a-directive
 "Isolating the Scope of a Directive"} section for more information about isolate scopes.
 </div>