[Quant][PT2E] Remove x86 inductor pt2e backend config (#105039)
**Summary**
For the Quantization PT2E path, we recommend to use `X86InductorQuantizer` instead of backend config of `x86_inductor_pt2e_backend_config`. Remove the `x86_inductor_pt2e_backend_config` and the relevant testing.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/105039
Approved by: https://github.com/jgong5, https://github.com/jerryzh168
