minor #5290 Overriding 3rd party bundles (anacicconi)

This PR was submitted for the 2.7 branch but it was merged into the 2.3 branch instead (closes #5290).

Discussion
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Overriding 3rd party bundles

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets | #4635

Commits
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58bb3c5 overriding 3rd party bundles

Author: weaverryan

best_practices/creating-the-project.rst

@@ -110,6 +110,13 @@ Symfony documentation uses the AppBundle name.
     There is no need to prefix the AppBundle with your own vendor (e.g.
     AcmeAppBundle), because this application bundle is never going to be
     shared.
+    
+.. note::
+    
+    Another reason to create a new bundle is when you're overriding something 
+    in a vendor's bundle. For instance, if you have to override an action of 
+    the FOSUserBundle, then you should create a UserBundle that would be used 
+    only for this purpose. 
 
 All in all, this is the typical directory structure of a Symfony application
 that follows these best practices: