Config.pm: switch GitHub from git: to https:

Config.pm: switch GitHub from git: to https:

In 1b75a119ab39 (Config.pm: modernize config example settings,
2016-03-29), the mirror source for GitHub was switched from git: to
https: on the master branch, but git: was retained on the rorcz branch.

There's no good reason to retain the git: scheme when setting up GitHub
mirrors and several good reasons to switch to https:

  * Should GitHub support redirects (perhaps in the case of a project
    rename), they can be followed whereas git: has no redirects.

  * We set a low speed timeout limit via cURL for http:/https: fetch
    but do not have such a thing available for git: so the full jobd.pl
    job timeout must expire for git: fetches that hang but not
    http:/https:.

  * The https: scheme is secure from unwanted interference whereas the
    git: scheme is not.

Therefore switch the GitHub mirror source from git: to https: to match
what's on the master branch.

Signed-off-by: Kyle J. McKay <mackyle@gmail.com>