调用以下命令后：
sudo apt-get update
sudo apt-get upgrade
我收到以下错误：
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following packages have been kept back:
linux-generic-hwe-20.04 linux-headers-generic-hwe-20.04 linux-image-generic-hwe-20.04
The following packages will be upgraded:
libproxy1-plugin-gsettings libproxy1-plugin-networkmanager libproxy1v5
3 upgraded, 0 newly installed, 0 to remove and 3 not upgraded.
Need to get 72.2 kB of archives.
After this operation, 4,096 B disk space will be freed.
Do you want to continue? [Y/n] Y
Get:1 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-networkmanager amd64 0.4.15-10ubuntu1.1 [5,288 B]
Ign:1 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-networkmanager amd64 0.4.15-10ubuntu1.1
Get:2 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-gsettings amd64 0.4.15-10ubuntu1.1 [18.1 kB]
Ign:2 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-gsettings amd64 0.4.15-10ubuntu1.1
Get:3 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1v5 amd64 0.4.15-10ubuntu1.1 [48.8 kB]
Ign:3 http://in.archive.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1v5 amd64 0.4.15-10ubuntu1.1
Get:1 http://security.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-networkmanager amd64 0.4.15-10ubuntu1.1 [5,288 B]
Err:1 http://security.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-networkmanager amd64 0.4.15-10ubuntu1.1
Undetermined Error [IP: 91.189.91.39 80]
Get:2 http://security.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-gsettings amd64 0.4.15-10ubuntu1.1 [18.1 kB]
Err:2 http://security.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1-plugin-gsettings amd64 0.4.15-10ubuntu1.1
Undetermined Error [IP: 91.189.91.39 80]
Get:3 http://security.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1v5 amd64 0.4.15-10ubuntu1.1 [48.8 kB]
Err:3 http://security.ubuntu.com/ubuntu focal-updates/main amd64 libproxy1v5 amd64 0.4.15-10ubuntu1.1
Undetermined Error [IP: 91.189.91.39 80]
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/libp/libproxy/libproxy1-plugin-networkmanager_0.4.15-10ubuntu1.1_amd64.deb Undetermined Error [IP: 91.189.91.39 80]
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/libp/libproxy/libproxy1-plugin-gsettings_0.4.15-10ubuntu1.1_amd64.deb Undetermined Error [IP: 91.189.91.39 80]
E: Failed to fetch http://security.ubuntu.com/ubuntu/pool/main/libp/libproxy/libproxy1v5_0.4.15-10ubuntu1.1_amd64.deb Undetermined Error [IP: 91.189.91.39 80]
E: Unable to fetch some archives, maybe run apt-get update or try with --fix-missing?
我该如何修复它？