minor #11129 use :: instead of .. code-block:: php (OskarStark)

This PR was merged into the 3.4 branch.

Discussion
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use :: instead of .. code-block:: php

Follow up of #11125

cc @javiereguiluz

Commits
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d6cbee9 use :: instead of .. code-block:: php

Author: javiereguiluz

reference/forms/types/collection.rst

@@ -371,9 +371,7 @@ prototype_data
 
 Allows you to define specific data for the prototype. Each new row added will
 initially contain the data set by this option. By default, the data configured
-for all entries with the `entry_options`_ option will be used.
-
-.. code-block:: php
+for all entries with the `entry_options`_ option will be used::
 
     use Symfony\Component\Form\Extension\Core\Type\CollectionType;
     use Symfony\Component\Form\Extension\Core\Type\TextType;