Update channels_last memory format tutorial (#3434) #4725

Job	Run time
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	15m 42s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	40m 27s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	22m 17s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	15m 28s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	14m 0s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 17s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	15m 25s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	16m 52s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	20m 56s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	28m 1s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	15m 38s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	26m 27s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	19m 6s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	32m 59s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	16m 27s
pytorch_tutorial_build_manager	22m 16s
	5h 43m 18s

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