Add a comment for the future

Author: encukou

Python/optimizer.c

@@ -109,6 +109,7 @@ uop_optimize(_PyInterpreterFrame *frame, _Py_CODEUNIT *instr,
 /* Returns 1 if optimized, 0 if not optimized, and -1 for an error.
  * If optimized, *executor_ptr contains a new reference to the executor
  */
+// gh-137573: inlining this function causes stack overflows
 Py_NO_INLINE int
 _PyOptimizer_Optimize(
     _PyInterpreterFrame *frame, _Py_CODEUNIT *start,