[test] call sphinx once per tutorial file #4389

Job	Run time
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	15m 2s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	15m 6s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	14m 43s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	15m 45s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	14m 48s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	14m 56s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	14m 59s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	14m 54s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	14m 54s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	18m 41s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	14m 52s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	18m 40s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	18m 48s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	14m 39s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	18m 49s
pytorch_tutorial_build_manager	0s
	3h 59m 36s

Provide feedback