[AIRFLOW-XXX] Fix wrong {{ next_ds }} description (#4017)

docs/code.rst

@@ -251,7 +251,7 @@ Variable                            Description
 ``{{ prev_ds_nodash }}``            the previous execution date as ``YYYYMMDD`` if exists, else ``None`
 ``{{ next_ds }}``                   the next execution date as ``YYYY-MM-DD``
                                     if ``{{ ds }}`` is ``2016-01-01`` and ``schedule_interval`` is ``@weekly``,
-                                    ``{{ prev_ds }}`` will be ``2016-01-08``
+                                    ``{{ next_ds }}`` will be ``2016-01-08``
 ``{{ next_ds_nodash }}``            the next execution date as ``YYYYMMDD`` if exists, else ``None`
 ``{{ yesterday_ds }}``              yesterday's date as ``YYYY-MM-DD``
 ``{{ yesterday_ds_nodash }}``       yesterday's date as ``YYYYMMDD``