Very often, I'd wake up, to which point there's a new Nightly release
out, and the update button would be stuck in the "Downloading..." step.
It'd only immediately change its state to "Restart" once I quit the app
and re-open it again. Turns out we were just missing a cx.notify in the
callback to trigger a re-render.

Release Notes:

- Fixed a bug where the update version button would be stuck in the
"Downloading..." step.