[quant][fix] Fix quantization for sub_scalar (#64603)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/64603
We'll insert observer only when both the operator and dtype is supported
Test Plan:
python test/test_quantization.py TestQuantizeFx.test_sub_scalar
Imported from OSS
Reviewed By: vkuzo
Differential Revision: D30797025
fbshipit-source-id: a77c21e2749405534fc245374cf33a0657a3d2c8
