Add note about default_auto_wrap_policy -> size_based_auto_wrap_policy

Author: davidberard98

intermediate_source/FSDP_tutorial.rst

@@ -62,6 +62,9 @@ We add the following code snippets to a python script “FSDP_mnist.py”.
 
 1.2  Import necessary packages
 
+.. note::
+    This tutorial is intended for pytorch versions 1.12 and later. If you are using 1.11 or earlier, replace all instances of `size_based_auto_wrap_policy` with `default_auto_wrap_policy`.
+
 .. code-block:: python
 
     # Based on: https://github.com/pytorch/examples/blob/master/mnist/main.py