minor symfony#12977 Update service_container.rst (l-vo)

This PR was merged into the 5.0 branch.

Discussion
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Update service_container.rst

Controller base class doesn't exist anymore in SF 5.0

Commits
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3d75d9a Update service_container.rst

Author: javiereguiluz

service_container.rst

@@ -812,7 +812,7 @@ this file is ``public: false`` by default.
 
 What does this mean? When a service **is** public, you can access it directly
 from the container object, which is accessible from any controller that extends
-``Controller``::
+:class:`Symfony\\Bundle\\FrameworkBundle\\Controller\\AbstractController`::
 
     use App\Service\MessageGenerator;