Update file U-Net3D.def

MLPerf/training/image_segmentation/pytorch/U-Net3D.def

@@ -12,6 +12,10 @@ export PYTHONNOUSERSITE=True
 mkdir -p /workspace/unet3d
 cd /workspace/unet3d
 
+apt-key del 7fa2af80
+apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64/3bf863cc.pub
+apt-key adv --fetch-keys https://developer.download.nvidia.com/compute/machine-learning/repos/ubuntu2004/x86_64/7fa2af80.pub
+
 apt-get update && \
     apt-get upgrade -y && \
     apt-get install -y git