standardize on HTTPS for github.com links
standardize on HTTPS for github.com links

fdroid link already checks HTTPS in build metadata, so this should also use
HTTPS.  It makes firewall rules easier when everything is HTTPS.

f-droid/fdroid-server,f-droid/fdroid-server,fdroidtravis/fdroidserver,f-droid/fdroid-server,matlink/fdroidserver,f-droid/fdroidserver,matlink/fdroidserver,matlink/fdroidserver,f-droid/fdroidserver,matlink/fdroidserver,fdroidtravis/fdroidserver,fdroidtravis/fdroidserver,f-droid/fdroid-server,matlink/fdroidserver,f-droid/fdroidserver,f-droid/fdroid-server,f-droid/fdroidserver,f-droid/fdroidserver,fdroidtravis/fdroidserver