Fix values class references

Author: lex111

reference/twig_reference.rst

@@ -762,8 +762,8 @@ needed objects and values. It is an instance of
 The available attributes are:
 
 * ``app.user``, a PHP object representing the current user;
-* ``app.request``, a :class:``Symfony\\Component\\HttpFoundation\\Request`` object;
-* ``app.session``, a :class:``Symfony\\Component\\HttpFoundation\\Session\\Session`` object;
+* ``app.request``, a :class:`Symfony\\Component\\HttpFoundation\\Request` object;
+* ``app.session``, a :class:`Symfony\\Component\\HttpFoundation\\Session\\Session` object;
 * ``app.environment``, a string with the name of the execution environment;
 * ``app.debug``, a boolean telling whether the debug mode is enabled in the app;
 * ``app.security`` (deprecated as of 2.6).