minor #8127 Fixed the explanation about PHPUnit event listeners in PHPUnitBridge (javiereguiluz)

This PR was squashed before being merged into the 2.7 branch (closes #8127).

Discussion
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Fixed the explanation about PHPUnit event listeners in PHPUnitBridge

This fixes #7411.

@nicolas-grekas if you have some time, please review this change. Thanks!

Commits
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29c830b Fixed the explanation about PHPUnit event listeners in PHPUnitBridge

Author: xabbuh

components/phpunit_bridge.rst

@@ -37,10 +37,16 @@ You can install the component in 2 different ways:
 Usage
 -----
 
-Once the component is installed, it automatically registers a
-`PHPUnit event listener`_ which in turn registers a `PHP error handler`_
-called :class:`Symfony\\Bridge\\PhpUnit\\DeprecationErrorHandler`. After
-running your PHPUnit tests, you will get a report similar to this one:
+Once the component is installed, a ``simple-phpunit`` script is created in the
+``vendor/`` directory to run tests. This script wraps the original PHPUnit binary
+to provide more features:
+
+.. code-block:: terminal
+
+    $ cd my-project/
+    $ ./vendor/bin/simple-phpunit
+
+After running your PHPUnit tests, you will get a report similar to this one:
 
 .. image:: /_images/components/phpunit_bridge/report.png
 
@@ -57,6 +63,21 @@ The summary includes:
     Deprecation notices are all other (non-legacy) notices, grouped by message,
     test class and method.
 
+.. note::
+
+    If you don't want to use the ``simple-phpunit`` script, register the following
+    `PHPUnit event listener`_ in your PHPUnit configuration file to get the same
+    report about deprecations (which is created by a `PHP error handler`_
+    called :class:`Symfony\\Bridge\\PhpUnit\\DeprecationErrorHandler`):
+
+    .. code-block:: xml
+
+        <!-- phpunit.xml.dist -->
+        <!-- ... -->
+        <listeners>
+            <listener class="Symfony\Bridge\PhpUnit\SymfonyTestsListener" />
+        </listeners>
+
 Trigger Deprecation Notices
 ---------------------------