GitHub leaked git SSH server private key 😱 https://github.blog/2023-03-23-we-updated-our-rsa-ssh-host-key/ Spoiler: says

We have no reason to believe that the exposed key was abused and took this action out of an abundance of caution.

Also includes instructions how to tell your SSH client to drop the compromised old public key so you can verify and start trusting the new key. AFAIK your SSH client should not normally be using this key, you are most likely using an EC* key instead.