First of all, this is violating security rules, but anyway, you can do it.

Modify ~/.ssh/config like this:

Host raspberrypi
        HostName localhost
        UserKnownHostsFile=/dev/null
        StrictHostKeyChecking=no

When experimenting with vms and if you are destroying and re-build vms frequently, you might see this warning messages a lot, so, it might be helpful someday.

I found it here