[test] call sphinx once per tutorial file #4413

Job	Run time
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	15m 29s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	47m 0s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	1h 29m 46s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	24m 9s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	35m 13s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	1h 3m 20s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	1h 1m 18s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	35m 12s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	49m 9s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	22m 2s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	56m 26s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	50m 26s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	1h 2m 30s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	1h 11m 45s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	1h 2m 18s
pytorch_tutorial_build_manager	21m 18s
	12h 47m 21s

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