Update autograd_tutorial.py #4475

Job	Run time
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 45s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	17m 34s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	15m 18s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	15m 23s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	22m 38s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	32m 8s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	25m 57s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	20m 41s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	23m 12s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	16m 40s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	19m 26s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	39m 48s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	28m 17s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	19m 22s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	35m 53s
pytorch_tutorial_build_manager	22m 57s
	6h 16m 59s

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