Remove sphinx theme from .gitmodules #2835

Job	Run time
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	14m 24s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	51m 59s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	20m 59s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	29m 29s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	19m 40s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	17m 12s
pytorch_tutorial_build_worker (7, 15, linux.4xlarge.nvidia.gpu)	20m 0s
pytorch_tutorial_build_worker (8, 15, linux.4xlarge.nvidia.gpu)	18m 42s
pytorch_tutorial_build_worker (9, 15, linux.4xlarge.nvidia.gpu)	31m 44s
pytorch_tutorial_build_worker (10, 15, linux.4xlarge.nvidia.gpu)	23m 20s
pytorch_tutorial_build_worker (11, 15, linux.4xlarge.nvidia.gpu)	40m 4s
pytorch_tutorial_build_worker (12, 15, linux.4xlarge.nvidia.gpu)	18m 49s
pytorch_tutorial_build_worker (13, 15, linux.4xlarge.nvidia.gpu)	18m 58s
pytorch_tutorial_build_worker (14, 15, linux.4xlarge.nvidia.gpu)	11m 29s
pytorch_tutorial_build_worker (15, 15, linux.4xlarge.nvidia.gpu)	19m 23s
pytorch_tutorial_build_manager	18m 40s
	6h 14m 52s

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