[test] call sphinx once per tutorial file #4350

Job	Run time
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	33m 36s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	16m 15s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	21m 16s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	20m 17s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	22m 35s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	18m 34s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	19m 52s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	33m 6s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	21m 25s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	26m 54s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	23m 51s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	15m 5s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	22m 37s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	15m 1s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	28m 39s
pytorch_tutorial_build_manager	1s
	5h 39m 4s

Provide feedback