Remove Duplicate Dequant Node Pass (#4169)

Summary:
Pull Request resolved: https://github.com/pytorch/executorch/pull/4169

The original need for the DuplicateDequantNode pass was to correctly partition quantized ops. If the output of quantized ops were used twice, then a single dequant node would be reused by multiple ops. This made it impossible to partition for quantized ops using pattern based matching.

However, now that we have moved to source-based partitioner, we no longer need the dequant node pass before partitioning

Reviewed By: digantdesai, kirklandsign

Differential Revision: D46919620

fbshipit-source-id: 61071c6477817e0ab46df8aa02f896af0cb5043c