Removed 'U' from the documentation for Py_BuildValue to bring it in line

with the elimination of 'U' in modsupport.c on 2000/04/28 (replaced
with 'u' and 'u#' per fdrake's comments).

Doc/api/utilities.tex

@@ -827,9 +827,6 @@ PyArg_ParseTuple(args, "O|O:ref", &object, &callback)
     \item[\samp{S} (object) {[PyObject *]}]
     Same as \samp{O}.
 
-    \item[\samp{U} (object) {[PyObject *]}]
-    Same as \samp{O}.
-
     \item[\samp{N} (object) {[PyObject *]}]
     Same as \samp{O}, except it doesn't increment the reference count
     on the object.  Useful when the object is created by a call to an