[Toolbox] Change from GitHub's SSH key fingerprints to HTTPS Call

[adong]

What happened: It's a constant battle to catch up and updating with GitHub's SSH key fingerprints from docs.github.com/en/authentication/keeping-your-account-and-data-secure/githubs-ssh-key-fingerprints

see PR https://github.com/screwdriver-cd/toolbox/pull/32

What you expected to happen: If we have a better way to address such an issue, then we should implement it. For example, use the http/s protocol with GitHub token and commit things back rather than using ssh protocol. (without ssh, then ssh-key-fingerprints is not needed)

How to reproduce it: n/a