[test] call sphinx once per tutorial file #4407

Job	Run time
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	54m 50s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	31m 7s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	34m 18s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	14m 31s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	56m 34s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	21m 57s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	59m 20s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	50m 27s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	55m 28s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	1h 3m 11s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	1h 2m 3s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 23s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	1h 4m 3s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	48m 14s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	45m 31s
pytorch_tutorial_build_manager	1s
	11h 22m 58s

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