Update the quantization location in the executorch_stack (#380)

Summary:
Pull Request resolved: #380

The quantization happens on the autograd safe ATen dialect, instead of the core ATen Dialect. Hence update the location of it in the diagram.

Reviewed By: kimishpatel

Differential Revision: D49351678

fbshipit-source-id: 28cd08bbe7be6e47782273ee69f86a88bd2e18d4

Author: Martin Yuan