ns for fx: move relatedness mapping to mappings file (#57171)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/57171
No logic change, just moving the mapping to a file where
the other mappings are.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
```
Imported from OSS
Reviewed By: jerryzh168
Differential Revision: D28077978
fbshipit-source-id: 4049d6a498156a5dffe3a03d2f4abc79da7bf907
