[doc][c10d] Fixes to FSDP tutorial #3312

Job	Run time
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	11m 19s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	49m 58s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	18m 36s
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	29m 30s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	19m 41s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	24m 0s
pytorch_tutorial_build_worker (7, 15, linux.4xlarge.nvidia.gpu)	17m 58s
pytorch_tutorial_build_worker (8, 15, linux.4xlarge.nvidia.gpu)	13m 30s
pytorch_tutorial_build_worker (9, 15, linux.4xlarge.nvidia.gpu)	17m 19s
pytorch_tutorial_build_worker (10, 15, linux.4xlarge.nvidia.gpu)	15m 11s
pytorch_tutorial_build_worker (11, 15, linux.4xlarge.nvidia.gpu)	25m 41s
pytorch_tutorial_build_worker (12, 15, linux.4xlarge.nvidia.gpu)	26m 34s
pytorch_tutorial_build_worker (13, 15, linux.4xlarge.nvidia.gpu)	37m 15s
pytorch_tutorial_build_worker (14, 15, linux.4xlarge.nvidia.gpu)	22m 51s
pytorch_tutorial_build_worker (15, 15, linux.4xlarge.nvidia.gpu)	16m 56s
pytorch_tutorial_build_manager	19m 44s
	6h 6m 3s

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