SystemExit_init(): avoid an useless test

Make silent a false positive of the Clang Static Analyzer.

Objects/exceptions.c

@@ -499,7 +499,7 @@ SystemExit_init(PySystemExitObject *self, PyObject *args, PyObject *kwds)
     Py_CLEAR(self->code);
     if (size == 1)
         self->code = PyTuple_GET_ITEM(args, 0);
-    else if (size > 1)
+    else /* size > 1 */
         self->code = args;
     Py_INCREF(self->code);
     return 0;