So, I have an old chromebook that I use as a thin client (first generation - no, not a CR-48).  Problem is, RSA keys change and I don't have a proper shell.  Just 'secure shell'.  This command removes a known host from the known_hosts file.  src.

Open up Secure Shell as a browser tab.  Go
'that-funny-button-for-misc-options' --> More Tools--> Developer Tools
Go to the Console tab.  In the console, enter the following, where foo is the index number of the host record that you need to remove.
term_.command.removeKnownHostByIndex(foo)