GitHub の ssh ホスト鍵がアップデートされとるがな！

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@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @
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IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!
Someone could be eavesdropping on you right now (man-in-the-middle attack)!
It is also possible that a host key has just been changed.
The fingerprint for the RSA key sent by the remote host is
SHA256:uNiVztksCsDhcc0u9e8BujQXVUpKZIDTMczCvj3tD2s.
Please contact your system administrator.
Add correct host key in /home/usename/.ssh/known_hosts to get rid of this message.
Offending RSA key in /home/usename/.ssh/known_hosts:x
  remove with:
  ssh-keygen -f "/home/usename/.ssh/known_hosts" -R "github.com"
Host key for github.com has changed and you have requested strict checking.
Host key verification failed.
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

$ ssh-keygen -f "/home/usename/.ssh/known_hosts" -R "github.com"
# Host github.com found: line x
/home/usename/.ssh/known_hosts updated.
Original contents retained as /home/usename/.ssh/known_hosts.old