Fix uniqueness check in movedim (#44307)
Summary:
Noticed this bug in `torch.movedim` (https://github.com/pytorch/pytorch/issues/41480). [`std::unique`](https://en.cppreference.com/w/cpp/algorithm/unique) only guarantees uniqueness for _sorted_ inputs. The current check lets through non-unique values when they aren't adjacent to each other in the list, e.g. `(0, 1, 0)` wouldn't raise an exception and instead the algorithm fails later with an internal assert.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/44307
Reviewed By: mrshenli
Differential Revision: D23598311
Pulled By: zou3519
fbshipit-source-id: fd6cc43877c42bb243cfa85341c564b6c758a1bf
