[QA] Keymap initial window size doesn't work too well on a 1024x600 screen

[-Meanwhile-]

Seen on hrev52849 x86_gcc2:

The Keymap preference application has an initial size that turns out a bit small for a 1024x600 screen.

Keys like PRINT, SCREEN, HOME are hard to read in this resolution, and lit indicators of num, caps and scroll are too easy to miss (the screenshot shows them clearer than in reality).