bug #3519 [Book][Service Container] Fix syntax highlighting (iamdto)

This PR was merged into the 2.4 branch.

Discussion
----------

[Book][Service Container] Fix syntax highlighting

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | 2.4+
| Fixed tickets | -

Commits
-------

edec44d [Book][Service Container] Fix syntax highlighting

book/service_container.rst

@@ -874,7 +874,7 @@ Now, just inject the ``request_stack``, which behaves like any normal service:
         # src/Acme/HelloBundle/Resources/config/services.yml
         services:
             newsletter_manager:
-                class:     "Acme\HelloBundle\Newsletter\NewsletterManager"
+                class:     Acme\HelloBundle\Newsletter\NewsletterManager
                 arguments: ["@request_stack"]
 
     .. code-block:: xml