Reduce the size of the update prompt

[Felanbird]

Description

I just randomly cut the width in half and it worked perfectly

I had to resize chatterino to the absolute minimum possible and put it on the bottom of my screen to be once again unable to interact with install/dismiss buttons while using this resolution.

Default sized window:

Full-screen:

Minimum possible width:

Fixes #2123

[Felanbird]

It dawned on me that the your version of chatterino is newer than the current stable prompt is a little long, forcing some new lines into the text does re-fit it to this small window but it does look a little cluttered, but it doesn't seem that bad