[qunat][fx] Remove "additional_fuser_method_mapping" key from prepare_custom_config_dict (#75388)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/75388
This is now replaced with backend_config_dict, we don't want to expose the implementation detail to
users. We'll have docs for backend_config_dict later
Test Plan:
python test/test_quantization.py TestQuantizeFx
python test/test_quantization.py TestQuantizeFxOps
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D35451958
fbshipit-source-id: 86e482d0782470ea02408836755cfc8531b8f66e
(cherry picked from commit 072541824b454e30df2b48758f465ebd814b436e)