Seems unnecessarily complicated, you can just `ssh-keygen -R` then `ssh git@github.com`, it should ask if you want to add the new key to the known hosts.
Also you should first check:
1. If you’re using GitHub’s rsa key at all
2. That you don’t have the other keys
In which case nuking all the keys is completely unnecessary, just remove the RSA one.
By comparing the fingerprint to a trusted source, which the snippet above doesn't do. And if you trust that the https source will lead you to the correct github, you can trivially check the fingerprint against what github publishes.
Also you should first check:
1. If you’re using GitHub’s rsa key at all
2. That you don’t have the other keys
In which case nuking all the keys is completely unnecessary, just remove the RSA one.