minor #7624 Add mention of the SymfonyTestsListener (theofidry, javiereguiluz)

This PR was submitted for the master branch but it was merged into the 3.2 branch instead (closes #7624).

Discussion
----------

Add mention of the SymfonyTestsListener

Follow up of symfony/symfony#21982 (comment).

/cc @xabbuh

Commits
-------

73dccd7 Fixed the issues reported by reviewers
ac8121d Removed an extra blank line
865ae6a Reworded the explanation
9263103 Add mention of the SymfonyTestsListener

Author: xabbuh

components/phpunit_bridge.rst

@@ -35,6 +35,24 @@ You can install the component in 2 different ways:
 
 .. include:: /components/require_autoload.rst.inc
 
+If you plan to :ref:`write-assertions-about-deprecations` and use the regular
+PHPUnit script (not the modified PHPUnit script provided by Symfony), you have
+to register a new `test listener`_ called ``SymfonyTestsListener``:
+
+.. code-block:: xml
+
+    <!-- http://phpunit.de/manual/6.0/en/appendixes.configuration.html -->
+    <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+             xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.0/phpunit.xsd"
+    >
+
+        <!-- ... -->
+
+        <listeners>
+            <listener class="Symfony\Bridge\PhpUnit\SymfonyTestsListener" />
+        </listeners>
+    </phpunit>
+
 Usage
 -----
 
@@ -94,9 +112,9 @@ message, enclosed with ``/``. For example, with:
 
 .. code-block:: xml
 
-    <!-- http://phpunit.de/manual/4.1/en/appendixes.configuration.html -->
+    <!-- http://phpunit.de/manual/6.0/en/appendixes.configuration.html -->
     <phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
-             xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/4.1/phpunit.xsd"
+             xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.0/phpunit.xsd"
     >
 
         <!-- ... -->
@@ -133,6 +151,8 @@ completely disable the deprecation helper. This is useful to make use of the
 rest of features provided by this component without getting errors or messages
 related to deprecations.
 
+.. _write-assertions-about-deprecations:
+
 Write Assertions about Deprecations
 -----------------------------------
 
@@ -401,3 +421,4 @@ If you have installed the bridge through Composer, you can run it by calling e.g
 .. _`@-silencing operator`: http://php.net/manual/en/language.operators.errorcontrol.php
 .. _`@-silenced`: http://php.net/manual/en/language.operators.errorcontrol.php
 .. _`Travis CI`: https://travis-ci.org/
+.. _`test listener`: https://phpunit.de/manual/current/en/appendixes.configuration.html#appendixes.configuration.test-listeners