Remove MNIST for XLA (#53274)
Summary:
Mitigates https://github.com/pytorch/pytorch/issues/53267
Pull Request resolved: https://github.com/pytorch/pytorch/pull/53274
Reviewed By: zhangguanheng66, ailzhang
Differential Revision: D26819702
Pulled By: cpuhrsch
fbshipit-source-id: 5b9b30db6f8fc414aa9f3c841429bf99bc927763
