Verify flatten works for quantized Tensor (#23121)
Summary:
Added a test in `test_torch.py`
Pull Request resolved: https://github.com/pytorch/pytorch/pull/23121
ghstack-source-id: 86983227
Differential Revision: D16391409
fbshipit-source-id: 04e72b2f753a0a6ddbf58d55b794e443b18a2156
