minor #4073 Reworded bundle requirement (WouterJ)

This PR was merged into the 2.3 branch.

Discussion
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Reworded bundle requirement

I can remember that we talked about this one, but I can't find it anymore. If anyone spots a PR which is already fixing this, I'll close this one a.s.a.p.

| Q   | A
| --- | ---
| Doc fix? | yes
| New docs? | no
| Applies to | all
| Ficket tickets | not sure

Commits
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b6f921b Reworded bundle requirement

cookbook/security/entity_provider.rst

@@ -25,8 +25,14 @@ Finally, the tutorial will demonstrate how to create a custom
 :class:`Symfony\\Bridge\\Doctrine\\Security\\User\\EntityUserProvider` object to
 retrieve users from a database with custom conditions.
 
-This tutorial assumes there is a bootstrapped and loaded
-``Acme\UserBundle`` bundle in the application kernel.
+.. sidebar:: Code along with the Example
+
+    If you want to follow along with the example in this chapter, create
+    an AcmeUserBundle via:
+
+    .. code-block:: bash
+
+        $ php app/console generate:bundle --namespace=Acme/UserBundle
 
 The Data Model
 --------------