Revamping the release process

[zeke]

@codebytere and I cut a new release today! https://github.com/electron/electron-api-demos/releases/tag/v1.4.0

Here's some followup work we need to do:

• decommission old update server
• remove update server deployment stuff from demo release process
• remove update server deployment stuff from demo release docs
• release a new version and see if update.electronjs.org server is working
• switch to forge

[codebytere]

• [x] remove update server deployment stuff from demo release process
• [x] remove update server deployment stuff from demo release docs

have been completed!

[zeke]

☝️ #387