[quant] Remove some redundant entries in backend_config_dict for TensorRT (#70971)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/70971
"root_module" and "reference_quantized_module_for_root" are only used in convert, removed
them for fused module and qat module swapping configurations
We may be able to remove some other fields as well.
Test Plan:
python test/fx2trt/test_quant_trt.py TestQuantizeFxTRTOps
Imported from OSS
Reviewed By: andrewor14
Differential Revision: D33470739
fbshipit-source-id: 67e6d58d7a3ec9fbd8c13527e701c06119aeb219
