Typo in field names in the `CheckSuite` struct

[alexandear]

The struct github.CheckSuite contains two fields with typos:

• Rerequstable -> Rerequestable (because json:"rerequestable")
• RunsRerequstable -> RunsRerequestable (because json:"runs_rerequestable")

The issue is easy to fix, but this will break backward compatibility. That's why I created the issue and I'm not sure if we should fix it.

[gmlewis]

Yes, let's please fix it... because we have other breaking API changes that can all go together into the next major release.
Thank you, @alexandear, for finding and for checking, and I'm guessing for fixing shortly as well! 😂