remove manual disabled binding

Author: fmalcher

src/app/registration-form-2/registration-form-2.html

@@ -86,7 +86,7 @@ <h1>Version 2: Advanced Validation and Schema Patterns</h1>
 
   <label>
     Topics (multiple possible):
-    <select [disabled]="registrationForm.newsletterTopics().disabled()" [control]="registrationForm.newsletterTopics">
+    <select [control]="registrationForm.newsletterTopics">
       <option value=""></option>
       <option value="Angular">Angular</option>
       <option value="Vue">Vue</option>