bug symfony#9368 Fix RST syntax (fabpot)

This PR was merged into the 2.7 branch.

Discussion
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Fix RST syntax

Commits
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f47a48a fixed RST syntax

Author: fabpot

configuration/external_parameters.rst

@@ -124,7 +124,7 @@ You can now reference these parameters wherever you need them.
 
         </container>
 
-    ::
+    .. code-block:: php
 
         $container->loadFromExtension('doctrine', array(
             'dbal' => array(