GitHubさんRSAのSSHホスト鍵更新したの何年前だっけって探してみたら半年前くらいだったのわね
https://github.blog/2023-03-23-we-updated-our-rsa-ssh-host-key/
The GitHub Blog · We updated our RSA SSH host keyAt approximately 05:00 UTC on March 24, out of an abundance of caution, we replaced our RSA SSH host key used to secure Git operations for GitHub.com.