If you just want to remove the gap, just comment out lines 403-406 in screens.rpy. The gap is intentional in order to provide a visual distinction between the functionality for the user, and lumping them into one long list of buttons may cause worse user experience, but it's ultimately up to your preference. Let me know if there are any issues doing this.
EDIT: If you just want to reduce the gap, in line 404, change 0.95 to a lower number (e.: 0.85). This may take some trial and error to find the right position you want. The closer to 1.0 you get, the further down the screen it is.