How do I get rid of these errors when running apt-get update on Ubuntu?
I have tried asking ChatGPT. It provided answers, and I tried them but the issue still persists.

root@localhost:~# sudo apt-get update
Hit:1 http://security.ubuntu.com/ubuntu jammy-security InRelease
Hit:2 http://mirrors.linode.com/ubuntu jammy InRelease                                                          
Hit:3 http://mirrors.linode.com/ubuntu jammy-updates InRelease                                                  
Hit:4 http://mirrors.linode.com/ubuntu jammy-backports InRelease                                                
Get:5 https://packages.cloud.google.com/apt cloud-sdk InRelease [1,616 B]                                       
Hit:6 https://ppa.launchpadcontent.net/ondrej/php/ubuntu jammy InRelease
Err:5 https://packages.cloud.google.com/apt cloud-sdk InRelease
  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C0BA5CE6DC6315A3
Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://packages.cloud.google.com/apt cloud-sdk InRelease: The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C0BA5CE6DC6315A3
W: Failed to fetch https://packages.cloud.google.com/apt/dists/cloud-sdk/InRelease  The following signatures couldn't be verified because the public key is not available: NO_PUBKEY C0BA5CE6DC6315A3
W: Some index files failed to download. They have been ignored, or old ones used instead.