minor #4237 Finished #3886 (ahsio, WouterJ)

This PR was merged into the 2.3 branch.

Discussion
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Finished #3886

Replaces #3886

Commits
-------

01057ae Reverted removal, removed API links instead
0670f25 [2.3] Examples that points to the DataCollectorListener should be removed.

components/form/form_events.rst

@@ -83,7 +83,7 @@ The ``FormEvents::PRE_SET_DATA`` event is dispatched at the beginning of the
 .. sidebar:: ``FormEvents::PRE_SET_DATA`` in the Form component
 
     The ``collection`` form type relies on the
-    :class:`Symfony\\Component\\Form\\Extension\\Core\\EventListener\\ResizeFormListener`
+    ``Symfony\Component\Form\Extension\Core\EventListener\ResizeFormListener``
     subscriber, listening to the ``FormEvents::PRE_SET_DATA`` event in order
     to reorder the form's fields depending on the data from the pre-populated
     object, by removing and adding all form rows.
@@ -110,7 +110,7 @@ the form.
 
 .. sidebar:: ``FormEvents::POST_SET_DATA`` in the Form component
 
-    The :class:`Symfony\\Component\\Form\\Extension\\DataCollector\\EventListener\\DataCollectorListener`
+    The ``Symfony\Component\Form\Extension\DataCollector\EventListener\DataCollectorListener``
     class is subscribed to listen to the ``FormEvents::POST_SET_DATA`` event
     in order to collect information about the forms from the denormalized
     model and view data.
@@ -152,10 +152,10 @@ It can be used to:
 
 .. sidebar:: ``FormEvents::PRE_SUBMIT`` in the Form component
 
-    The :class:`Symfony\\Component\\Form\\Extension\\Core\\EventListener\\TrimListener`
+    The ``Symfony\Component\Form\Extension\Core\EventListener\TrimListener``
     subscriber subscribes to the ``FormEvents::PRE_SUBMIT`` event in order to
     trim the request's data (for string values).
-    The :class:`Symfony\\Component\\Form\\Extension\\Csrf\\EventListener\\CsrfValidationListener`
+    The ``Symfony\Component\Form\Extension\Csrf\EventListener\CsrfValidationListener``
     subscriber subscribes to the ``FormEvents::PRE_SUBMIT`` event in order to
     validate the CSRF token.
 
@@ -186,7 +186,7 @@ It can be used to change data from the normalized representation of the data.
 
 .. sidebar:: ``FormEvents::SUBMIT`` in the Form component
 
-    The :class:`Symfony\\Component\\Form\\Extension\\Core\\EventListener\\ResizeFormListener`
+    The ``Symfony\Component\Form\Extension\Core\EventListener\ResizeFormListener``
     subscribes to the ``FormEvents::SUBMIT`` event in order to remove the
     fields that need to be removed whenever manipulating a collection of forms
     for which ``allow_delete`` has been enabled.
@@ -218,10 +218,10 @@ It can be used to fetch data after denormalization.
 
 .. sidebar:: ``FormEvents::POST_SUBMIT`` in the Form component
 
-    The :class:`Symfony\\Component\\Form\\Extension\\DataCollector\\EventListener\\DataCollectorListener`
+    The ``Symfony\Component\Form\Extension\DataCollector\EventListener\DataCollectorListener``
     subscribes to the ``FormEvents::POST_SUBMIT`` event in order to collect
     information about the forms.
-    The :class:`Symfony\\Component\\Form\\Extension\\Validator\\EventListener\\ValidationListener`
+    The ``Symfony\Component\Form\Extension\Validator\EventListener\ValidationListener``
     subscribes to the ``FormEvents::POST_SUBMIT`` event in order to
     automatically validate the denormalized object, and update the normalized
     as well as the view's representations.