minor #12004 Class name is wrong according to the other examples (OskarStark)

This PR was merged into the 4.3 branch.

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Class name is wrong according to the other examples

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f6906e0 Class name is wrong according to the other examples

Author: OskarStark

service_container/alias_private.rst

@@ -157,7 +157,7 @@ or you decided not to maintain it anymore), you can deprecate its definition:
     .. code-block:: yaml
 
         app.mailer:
-            alias: '@AppBundle\Mail\PhpMailer'
+            alias: '@App\Mail\PhpMailer'
 
             # this will display a generic deprecation message...
             deprecated: true