ns for fx: remove ".stats" suffix (#52799)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/52799
We agreed that it's better to not add this, removing.
We can make Eager mode NS match this in a future PR.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
```
Imported from OSS
Reviewed By: hx89
Differential Revision: D26652638
fbshipit-source-id: 5baa51a6bf6de5632946417fe9fd3d0f3e78f7fa
