Have you ever faced this issue while a git clone or a ssh?
Are you struggling to solve the issue? Then you have to read the error message carefully once more. That error message itself gives you the solution to solve it.
You need to remove the old signature from known_hosts file. Be careful that all the verified signatures are stored in the same file, so you need to remove only the one which is related to the changed host. So you can use the command below for achieving this.
Replace the <user> with your logged in username and <example.com> with domain or ip address of the host you need to connect. Make sure that you are trying to connect with the authentic server.