Update channels_last memory format tutorial #4723

Job	Run time
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	14m 54s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	27m 24s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	19m 50s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	16m 56s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	15m 18s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	16m 32s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 28s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	27m 0s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	22m 25s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	21m 5s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	16m 27s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	37m 20s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	41m 7s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	15m 3s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	14m 53s
pytorch_tutorial_build_manager	22m 13s
	5h 49m 55s

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