minor #10480 Update to micro_kernel_trait.rst (Alienpruts, alexislefebvre)

This PR was merged into the 3.4 branch.

Discussion
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Update to micro_kernel_trait.rst

Whenever you make a change to the "autoload' section of the composer.json file (amongst others), you need to regenerate the autoload files using composer dumpautoload, otherwise your changes will not be seen.

More info :
https://getcomposer.org/doc/03-cli.md#dump-autoload-dumpautoload-

Sorry if the proposed changes are not marked up properly, haven't gotten the hang of Markup language just yet :)

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Commits
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cca8833 Update micro_kernel_trait.rst
fe2efd4 Update configuration/micro_kernel_trait.rst
aaa2b2b Update to micro_kernel_trait.rst

Author: xabbuh

configuration/micro_kernel_trait.rst

@@ -126,6 +126,14 @@ your ``composer.json`` file to load from there:
         }
     }
 
+Before going any further, you need to regenerate the autoload files! Your changes in the "autoload"
+section of the ``composer.json`` file will not be in effect until you run the following command:
+
+.. code-block:: bash
+
+    $ composer dump-autoload
+    
+    
 Now, suppose you want to use Twig and load routes via annotations. Instead of
 putting *everything* in ``index.php``, create a new ``app/AppKernel.php`` to
 hold the kernel. Now it looks like this::