[Regression] Tabs no longer fit on screen.

Before updating to 3.4.0, tabs were nice and small, and I could comfortably fit a lot (~16) of them on the width of my screen. However, now the tabs are really big and wide and I can fit only 8 or so on my screen. Because only so few fit on the screen, I'm having trouble finding them. I find myself having to seek through tabs and getting confused because tabs have different locations depending on where the've scrolled. I keep accidentally hitting the wrong tabs.

Compare e.g. this nice compact tab:
http://guake-project.org/img/screenshot2.jpg
With this huge wide tab:
https://user-images.githubusercontent.com/1808686/47109326-f586c400-d21b-11e8-8e23-f79e82a994a1.png

**Guake Version**: x11-terms/guake-3.4.0-r1
Please describe **your system**
* Linux distribution: Gentoo
* GNOME version: N/A
* XFCE version: xfce-base/xfce4-meta-4.12-r1
* GTK version(s): x11-libs/gtk-2.24.32-r1, x11-libs/gtk-3.24.1