Revert "fix batch_norm amp autocast" (#8547) #10703

Job	Run time
get-torch-commit	2s
Build PyTorch/XLA / build	34m 4s
Build docs / build-docs	1m 42s
CPU tests / test (benchmark_tests)	8m 44s
TPU tests / tpu-test	46m 12s
CPU tests / test (python_tests, xla_op1)	18m 10s
CPU tests / test (python_tests, xla_op2)	5m 47s
CPU tests / test (python_tests, xla_op3)	9m 16s
CPU tests / test (python_tests, torch_mp_op)	13m 24s
CPU tests / test (cpp_tests, cpp_tests1)	5m 31s
CPU tests / test (cpp_tests, cpp_tests2)	6m 7s
	2h 28m 59s

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