[quant][bug] Histogram observer bug fix with min == max (#40310)
Summary: Pull Request resolved: https://github.com/pytorch/pytorch/pull/40310
Test Plan:
python test/test_quantization.py test_histogram_observer_same_inputs
Imported from OSS
Differential Revision: D22145908
fbshipit-source-id: c1646d9ae6738755981fe3d09c8a8e25fcb994d4
