[test] call sphinx once per tutorial file #4372

Job	Run time
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	15m 3s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	25m 22s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	22m 8s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	47m 30s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	22m 52s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	42m 3s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	21m 40s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	32m 34s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	17m 8s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	1h 4m 59s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	13m 17s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	1h 8m 9s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	29m 36s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	1h 0m 28s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	1h 4m 34s
pytorch_tutorial_build_manager	1s
	9h 7m 24s

Provide feedback