Fixed an RST syntax issue

Author: javiereguiluz

reference/constraints/File.rst

@@ -8,7 +8,7 @@ Validates that a value is a valid "file", which can be one of the following:
 * A valid :class:`Symfony\\Component\\HttpFoundation\\File\\File` object
   (including objects of :class:`Symfony\\Component\\HttpFoundation\\File\\UploadedFile` class).
 
-This constraint is commonly used in forms with the :doc:`FileType <reference/forms/types/file>`
+This constraint is commonly used in forms with the :doc:`FileType </reference/forms/types/file>`
 form field.
 
 .. tip::