minor #9509 Typo fix (I believe) (ebuildy)

This PR was submitted for the 4.0 branch but it was merged into the 3.4 branch instead (closes #9509).

Discussion
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Typo fix (I believe)

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Commits
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df2f3e4 Typo fix (I believe)

Author: javiereguiluz

service_container/service_decoration.rst

@@ -63,7 +63,7 @@ that you can reference it:
 
             AppBundle\DecoratingMailer:
                 # overrides the AppBundle\Mailer service
-                # but that service is still available as AppBundle\Mailer.inner
+                # but that service is still available as AppBundle\DecoratingMailer.inner
                 decorates: AppBundle\Mailer
 
                 # pass the old service as an argument