Minor wording change.

Doc/api/newtypes.tex

@@ -1322,7 +1322,7 @@ int tp_is_gc(PyObject *self)
 
 The remaining fields are only defined if the feature test macro
 \constant{COUNT_ALLOCS} is defined, and are for internal use only.
-They are documented here for completion.  None of these fields are
+They are documented here for completeness.  None of these fields are
 inherited by subtypes.
 
 \begin{cmemberdesc}{PyTypeObject}{int}{tp_allocs}