[test] call sphinx once per tutorial file #4351

Job	Run time
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	9m 36s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	9m 39s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	10m 9s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	9m 4s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	7m 31s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	9m 15s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	9m 10s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	7m 30s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	9m 12s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	9m 14s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	7m 30s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	9m 5s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	7m 32s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	7m 28s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	9m 4s
pytorch_tutorial_build_manager	-1s
	2h 10m 58s

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