[MPS] Fix `test_embedding_dense_backward` (#88847)
By copying randomly initialized weights distribution from MPS `nn.Embedding` to `cpu`
Test plan: `python test_mps.py -k test_embedding_dense_backward --repeat 150`
Fixes https://github.com/pytorch/pytorch/issues/88679
Pull Request resolved: https://github.com/pytorch/pytorch/pull/88847
Approved by: https://github.com/seemethere
