667ef9917f
This way "New Collection" is always assigned the same shortcut (N).
Whereas previously it would be automatically assigned the leftover key
from the list of available collections.
Nice side effect is that since N is next to M in most keyboard layouts,
moving to a new collection is super fast by hitting M then N.
{F8630575, size=full}
Paper-cut pointed out by DerekWatts on [devtalk](https://devtalk.blender.org/t/blender-ui-paper-cuts/2596/4211) (thanks!):
{F8630492, size=full}
Reviewed By: HooglyBoogly
Differential Revision: https://developer.blender.org/D8067