URLs to GitHub Actions API docs changed

[nightlark]

Various URLs to pages for the GitHub Actions related API docs have changed earlier today. The original links give page not found errors.

Of the sections listed for https://developer.github.com/v3/actions/ the changed URLs are:

• self_hosted_runners to self-hosted-runners
• workflow_jobs to workflow-jobs
• workflow_runs to workflow-runs

I sent an email to GitHub support to confirm that the change (without a redirect) was intentional, and mentioning that the link in a blog post made the same day is now broken.

[gmlewis]

Thank you, @nightlark!

[nightlark]

The change was intentional -- something about making the URLs more consistent (though the older docs are unchanged and many have underscores in the URL).

[gmlewis]

OK, thanks for reporting back, @nightlark!
I have added a new utility to this repo in #1477 that should be able to update all the URLs so don't worry about catching them all. After we get #1507 in, I can run it.