ns for fx: fix nit in default qlinear weight extraction function (#62334)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/62334
Removes the assert for node type in default qlinear weight extraction
function. Without the assert, user defined functions can now use
this util function without failing this check.
Test Plan:
```
python test/test_quantization.py TestFXNumericSuiteCoreAPIs
// further tests will be in follow-up fb-only diffs
```
Imported from OSS
Reviewed By: hx89
Differential Revision: D29963501
fbshipit-source-id: a634eabb5165375bde186438318ec52fa29c970f
