Update doctrine/associations.rst

Author: OskarStark

doctrine/associations.rst

@@ -581,7 +581,7 @@ also generated a ``removeProduct()`` method::
 Thanks to this, if you call ``$category->removeProduct($product)``, the ``category_id``
 on that ``Product`` will be set to ``null`` in the database.
 
-.. caution::
+.. warning::
 
     Please be aware that the inverse side could be associated with a large amount of records.
     I.e. there could be a large amount of products with the same category.