quantization: fix bug in QuantWrapper with DeQuant qconfig (#73671)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73671
QuantWrapper did not correctly apply qconfig to the dequant.
Therefore, if the user first applied qconfig to their module and
then wrapped it with `QuantWrapper`, the dequant would not get
swapped during the convert step.
The fix is to properly apply the qconfig to the dequant.
Test Plan:
```
python test/test_quantization.py TestQuantizeEagerPTQStatic.test_quantwrapper_attaches_qconfig_to_dequant
```
Reviewed By: MaigoAkisame
Differential Revision: D34585260
Pulled By: vkuzo
fbshipit-source-id: 82055a9fa7fc13a714fe460deb461c2e87e76b39
(cherry picked from commit c9f392333dd1c005d893bdc2fbafe8a82b317c88)
