Fix a minor syntax issue

Author: Javier Eguiluz

components/serializer.rst

@@ -825,9 +825,9 @@ The Serializer component provides several built-in normalizers:
     To convert the objects to integers or floats, set the serializer context option
     ``DateTimeNormalizer::CAST_KEY`` to ``int`` or ``float``.
 
-.. versionadded:: 7.1
+    .. versionadded:: 7.1
 
-    ``DateTimeNormalizer::CAST_KEY`` context option was introduced in Symfony 7.1.
+        ``DateTimeNormalizer::CAST_KEY`` context option was introduced in Symfony 7.1.
 
 :class:`Symfony\\Component\\Serializer\\Normalizer\\DateTimeZoneNormalizer`
     This normalizer converts :phpclass:`DateTimeZone` objects into strings that