Use cdn endpoint for auto update (#1538)
Use cdn endpoint for auto update (#1538)

This will make electron-updater use the cdn-fronted updates.signal.org instead
of the s3 endpoint. You can verify it worked by looking at the url generated in
dist/latest-mac.json and dist/win-unpacked/resources/app-update.yml

// FREEBIE
nrizzio/Signal-Desktop,nrizzio/Signal-Desktop,nrizzio/Signal-Desktop,nrizzio/Signal-Desktop