Remove legacy tensor constructors for complex dtypes
PR #72405 added four new types to the public python API:
`torch.ComplexFloatTensor`, `torch.ComplexDoubleTensor`,
`torch.cuda.ComplexFloatTensor` and `torch.cuda.ComplexDoubleTensor`.
I believe this was unintentional and a clarifying comment as to the
purpose of `all_declared_types` is needed to avoid this in future.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/73370
