Apply suggestion from @mnocon

Author: mnocon

docs/content_management/rich_text/create_custom_richtext_block.md

@@ -27,7 +27,7 @@ Create a `src/Event/Subscriber/RichTextBlockSubscriber.php` file.
 
 In line 28, `my_block` is the same name of the block that you defined in line 3 above.
 Line 28 also implements the `PreRender` method.
-Lines 41-51 handle the conversion of content into an XML string:
+Lines 37-47 handle the conversion of content into an XML string:
 
 ``` php hl_lines="28 37-47"
 [[= include_code('code_samples/back_office/online_editor/src/event/subscriber/RichTextBlockSubscriber.php') =]]