bpo-45439: Rename _PyObject_CallNoArg() to _PyObject_CallNoArgs() (GH-28891)

Fix typo in the private _PyObject_CallNoArg() function name: rename
it to _PyObject_CallNoArgs() to be consistent with the public
function PyObject_CallNoArgs().

Python/sysmodule.c

@@ -1676,7 +1676,7 @@ _PySys_GetSizeOf(PyObject *o)
         }
     }
     else {
-        res = _PyObject_CallNoArg(method);
+        res = _PyObject_CallNoArgs(method);
         Py_DECREF(method);
     }