Switch to USE_GITHUB.
fedorahosted.org is down and the project has switched to GitHub.
Comparing the GitHub tarball and the old one from distcache.FreeBSD.org, the
former has a few new files:
- .gitignore
- extras/img/omping-banner-url.svg
- extras/img/omping-banner.svg
- extras/img/omping-icon.svg
All the other contents are identical.
PR: 218099