minor symfony#8326 action_method.rst (atailouloute)

This PR was squashed before being merged into the 2.7 branch (closes symfony#8326).

Discussion
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action_method.rst

On the form documentation [How to Change the Action and Method of a Form](https://symfony.com/doc/current/form/action_method.html), the examples "Standalone use" contain `$this->generateUrl`which does not make sense, since we are not inside a controller

I though also about replacing by `...` since the important here is just to know how to change the action and not how to generate the route ..

Commits
-------

656b865 action_method.rst

Author: wouterj

form/action_method.rst

@@ -49,7 +49,7 @@ form, you can use ``setAction()`` and ``setMethod()``:
         $formFactory = $formFactoryBuilder->getFormFactory();
 
         $form = $formFactory->createBuilder('form', $task)
-            ->setAction($this->generateUrl('target_route'))
+            ->setAction('...')
             ->setMethod('GET')
             ->add('task', 'text')
             ->add('dueDate', 'date')
@@ -102,7 +102,7 @@ options:
         $formFactory = $formFactoryBuilder->getFormFactory();
 
         $form = $formFactory->create(new TaskType(), $task, array(
-            'action' => $this->generateUrl('target_route'),
+            'action' => '...',
             'method' => 'GET',
         ));