fix: progress bar for update on linux

[peter-sanderson]

Problem is, that for differential downloads, the progress bar is not working correctly (seems to not be implemented for multi-range downloads at all).

Solution is therefore to fallback to direct full download. However, the switch for this is simply not working for AppImage so we have to fix it in Electron Builder first.

Resolves: #14416

• This PR is related to this in Electron Repo: download-progress event not firing electron-userland/electron-builder#8659
• ❗ This fix: use disableDifferentialDownload flag in the AppImageBuilder electron-userland/electron-builder#8695 needs to be finished, merged and released first in the electron builder repo first.

[peter-sanderson]

🎉 electron-userland/electron-builder#8695 was merged! Now we need only wait for the release.