Correct Python docs example

Fix PyTuple_SetItem in argout typemap
Fix from Bob Hood on swig-user mailing list
[skip ci]

Doc/Manual/Python.html

@@ -4899,7 +4899,7 @@ A typemap can be used to handle this case as follows :
     if (!PyTuple_Check($result)) {
       PyObject *o2 = $result;
       $result = PyTuple_New(1);
-            PyTuple_SetItem(target,0,o2);
+      PyTuple_SetItem($result,0,o2);
     }
     o3 = PyTuple_New(1);
     PyTuple_SetItem(o3,0,o);