Don't error when dataset is already downloaded #3312

Job	Run time
linux (linux.12xlarge, cpu) / linux-job	4m 7s
linux (linux.g5.4xlarge.nvidia.gpu, cuda, 11.8) / linux-job	9m 8s
windows (windows.4xlarge, cpu) / windows-job	18m 2s
windows (windows.g5.4xlarge.nvidia.gpu, cuda, 11.8) / windows-job	13m 33s
macos (macos-m1-stable) / macos-job	7m 38s
	52m 28s

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