bug #5507 Path fixed (carlosreig)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5507).

Discussion
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Path fixed

Path fixed since TwigBridge v2.7 changed the folder structure

Commits
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8d7b5db Path fixed

Author: wouterj

components/form/introduction.rst

@@ -189,10 +189,10 @@ to bootstrap or access Twig and add the :class:`Symfony\\Bridge\\Twig\\Extension
     $defaultFormTheme = 'form_div_layout.html.twig';
 
     $vendorDir = realpath(__DIR__.'/../vendor');
-    // the path to TwigBridge so Twig can locate the
+    // the path to TwigBridge library so Twig can locate the
     // form_div_layout.html.twig file
-    $vendorTwigBridgeDir =
-        $vendorDir.'/symfony/twig-bridge/Symfony/Bridge/Twig';
+    $appVariableReflection = new \ReflectionClass('\Symfony\Bridge\Twig\AppVariable');
+    $vendorTwigBridgeDir = dirname($appVariableReflection->getFileName());
     // the path to your other templates
     $viewsDir = realpath(__DIR__.'/../views');