我在 AZURE 上启动了 NVIDIA VM 并尝试使用进行更新，
sudo apt update
但出现错误：
Hit:2 http://azure.archive.ubuntu.com/ubuntu focal InRelease
Hit:3 http://azure.archive.ubuntu.com/ubuntu focal-updates InRelease
Hit:4 http://azure.archive.ubuntu.com/ubuntu focal-backports InRelease
Hit:5 https://packages.microsoft.com/repos/azure-cli focal InRelease
Hit:6 http://security.ubuntu.com/ubuntu focal-security InRelease
Err:1 http://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64 InRelease
The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A4B469963BF863CC
Reading package lists... Done
W: GPG error: http://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64 InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY A4B469963BF863CC
E: The repository 'http://developer.download.nvidia.com/compute/cuda/repos/ubuntu2004/x86_64 InRelease' is no longer …