bug #4886 [Best Pracitices] restore example in the "Service: No Class…

… Parameter" section (u-voelkel)

This PR was merged into the 2.3 branch.

Discussion
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[Best Pracitices] restore example in the "Service: No Class Parameter" section

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

In 1fb20e5 the 'how to NOT do it' config example in the "Best Practices -> Organizing Your Business Logic -> Service: No Class Parameter" section was changed to actually follow the recommendation.
It is especially confusing as the example in the section "Services: Naming and Format" is exactly the same (besides the comment)

Commits
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0a678d2 fixed indentation
73ff5ea restore the how to NOT do it example in the "Service: No Class Parameter" section

best_practices/business-logic.rst

@@ -140,9 +140,12 @@ the class namespace as a parameter:
     # app/config/services.yml
 
     # service definition with class namespace as parameter
+    parameters:
+        slugger.class: AppBundle\Utils\Slugger
+
     services:
         app.slugger:
-            class: AppBundle\Utils\Slugger
+            class: "%slugger.class%"
 
 This practice is cumbersome and completely unnecessary for your own services: