Fix parent type doc reference

Author: bicpi

reference/forms/types/radio.rst

@@ -28,7 +28,7 @@ If you want to have a Boolean field, use :doc:`checkbox </reference/forms/types/
 |             | - `error_mapping`_                                                  |
 |             | - `mapped`_                                                         |
 +-------------+---------------------------------------------------------------------+
-| Parent type | :doc:`form </reference/forms/types/checkbox>`                       |
+| Parent type | :doc:`checkbox </reference/forms/types/checkbox>`                   |
 +-------------+---------------------------------------------------------------------+
 | Class       | :class:`Symfony\\Component\\Form\\Extension\\Core\\Type\\RadioType` |
 +-------------+---------------------------------------------------------------------+