Add note to not edit upstream_shape_helpers.py

python/torch_mlir/dialects/torch/importer/jit_ir/build_tools/upstream_shape_helpers.py

@@ -2,15 +2,16 @@
 # the PyTorch BSD-style license available at
 # https://github.com/pytorch/pytorch/blob/master/LICENSE
 
+# DO NOT EDIT THIS FILE, except by copying new upstream contents into it.
+# Code taken from torch/csrc/jit/runtime/symbolic_shape_registry.cpp
+# Once https://github.com/pytorch/pytorch/pull/68564 lands, we can directly
+# use the code from upstream.
+
 # Minimal imports needed for the code to compile.
 from typing import List, Any, Optional
 import torch
 number = float
 
-# Code taken from torch/csrc/jit/runtime/symbolic_shape_registry.cpp
-# Once https://github.com/pytorch/pytorch/pull/68564 lands, we can directly
-# use the code from upstream.
-
 ####     SHAPE COMPUTE FUNCTIONS    ###
 def broadcast(a: List[int], b: List[int]):
   dimsA = len(a)