Remove link to nonexisting target.

Doc/library/__builtin__.rst

@@ -8,7 +8,7 @@
 
 This module provides direct access to all 'built-in' identifiers of Python; for
 example, ``__builtin__.open`` is the full name for the built-in function
-:func:`open`.  See chapter :ref:`builtin`.
+:func:`open`.
 
 This module is not normally accessed explicitly by most applications, but can be
 useful in modules that provide objects with the same name as a built-in value,