ns for fx: allow comparing int8 to int8 for functionals (#57027)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57027
Fixes a bug to allow shadowing of linear and conv functionals.
The bug is to only detach tensors, not all objects.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs.test_int8_shadows_int8_fun
```
Reviewed By: jerryzh168
Differential Revision: D28030090
Pulled By: vkuzo
fbshipit-source-id: 0a38c4b232e007d7822eee818b0af99d98335d22
