minor edits in AR validations guide

railties/guides/source/active_record_validations_callbacks.textile

@@ -796,17 +796,9 @@ person.errors.size # => 0
 
 h3. Displaying Validation Errors in the View
 
-Rails maintains an official plugin, DynamicForm, that provides helpers to display the error messages of your models in your view templates. You can install it as a plugin or as a Gem.
+"DynamicForm":https://github.com/joelmoss/dynamic_form provides helpers to display the error messages of your models in your view templates.
 
-h4. Installing as a plugin
-
-<shell>
-$ rails plugin install git://github.com/joelmoss/dynamic_form.git
-</shell>
-
-h4. Installing as a Gem
-
-Add this line in your Gemfile:
+You can install it as a gem by adding this line to your Gemfile:
 
 <ruby>
 gem "dynamic_form"