Fix JSON parse error in Twig docs

doc/providers/twig.rst

@@ -60,7 +60,7 @@ some Symfony2 components and Twig. Add it as a dependency to your
 .. code-block:: json
 
     "require": {
-        "symfony/twig-bridge": "~2.1",
+        "symfony/twig-bridge": "~2.1"
     }
 
 When present, the ``TwigServiceProvider`` will provide you with the following