Fixing small rendering error - see #1398

Author: weaverryan

components/dependency_injection/tags.rst

@@ -150,7 +150,7 @@ Register the pass with the container
 ------------------------------------
 
 You also need to register the pass with the container, it will then be
-run when the container is compiled.
+run when the container is compiled::
 
     use Symfony\Component\DependencyInjection\ContainerBuilder;