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/bltinmodule.c

@@ -2305,7 +2305,7 @@ builtin_round_impl(PyObject *module, PyObject *number, PyObject *ndigits)
     }
 
     if (ndigits == Py_None)
-        result = _PyObject_CallNoArg(round);
+        result = _PyObject_CallNoArgs(round);
     else
         result = PyObject_CallOneArg(round, ndigits);
     Py_DECREF(round);