Update index.rst with whats new for 2.8 #5004

Job	Run time
pytorch_tutorial_build_worker (4, 15, linux.g5.4xlarge.nvidia.gpu)	32m 13s
pytorch_tutorial_build_worker (5, 15, linux.g5.4xlarge.nvidia.gpu)	22m 50s
pytorch_tutorial_build_worker (2, 15, linux.g5.4xlarge.nvidia.gpu)	37m 39s
pytorch_tutorial_build_worker (6, 15, linux.g5.4xlarge.nvidia.gpu)	35m 11s
pytorch_tutorial_build_worker (1, 15, linux.g5.12xlarge.nvidia.gpu)	14m 58s
pytorch_tutorial_build_worker (11, 15, linux.g5.4xlarge.nvidia.gpu)	14m 41s
pytorch_tutorial_build_worker (7, 15, linux.g5.4xlarge.nvidia.gpu)	22m 16s
pytorch_tutorial_build_worker (12, 15, linux.g5.4xlarge.nvidia.gpu)	16m 13s
pytorch_tutorial_build_worker (14, 15, linux.g5.4xlarge.nvidia.gpu)	29m 7s
pytorch_tutorial_build_worker (8, 15, linux.g5.4xlarge.nvidia.gpu)	25m 3s
pytorch_tutorial_build_worker (10, 15, linux.g5.4xlarge.nvidia.gpu)	17m 17s
pytorch_tutorial_build_worker (13, 15, linux.g5.4xlarge.nvidia.gpu)	15m 56s
pytorch_tutorial_build_worker (9, 15, linux.g5.4xlarge.nvidia.gpu)	19m 43s
pytorch_tutorial_build_worker (15, 15, linux.g5.4xlarge.nvidia.gpu)	19m 42s
pytorch_tutorial_build_worker (3, 15, linux.g5.4xlarge.nvidia.gpu)	24m 20s
pytorch_tutorial_build_manager	22m 9s
	6h 9m 18s

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