Revert "[xnnpack] Reexport after quantize in aot_compiler (#7714)"

This reverts commit 2f0518d.

Author: huydhn

examples/xnnpack/aot_compiler.py

@@ -92,7 +92,6 @@
         logging.info("Quantizing Model...")
         # TODO(T165162973): This pass shall eventually be folded into quantizer
         model = quantize(model, example_inputs)
-        ep = torch.export.export_for_training(model, example_inputs)
 
     edge = to_edge_transform_and_lower(
         ep,