minor #10839 Fix classes generation with YAML or XML metadata. (baiolo)

This PR was squashed before being merged into the 4.1 branch (closes #10839).

Discussion
----------

Fix classes generation with YAML or XML metadata.

The documentation misses the change of one configuration file if the generated metadata is in YAML or XML format. This PR documents how to change the configuration file.

Commits
-------

eb5cad3 Fix classes generation with YAML or XML metadata.

Author: xabbuh

doctrine/reverse_engineering.rst

@@ -70,6 +70,23 @@ files: ``BlogPost.php`` and ``BlogComment.php``.
 
         $ php bin/console doctrine:mapping:import 'App\Entity' xml --path=config/doctrine
 
+    In this case, make sure to adapt your mapping configuration accordingly:
+
+    .. code-block:: yaml
+
+        # config/packages/doctrine.yaml
+        doctrine:
+            # ...
+            orm:
+                # ...
+                mappings:
+                    App:
+                        is_bundle: false
+                        type: yml # Set to xml in case of XML mapping
+                        dir: '%kernel.project_dir%/config/doctrine'
+                        prefix: 'App\Entity'
+                        alias: App
+
 Generating the Getters & Setters or PHP Classes
 -----------------------------------------------