Gyroplast

That’s listed in the makedepends array of the PKGBUILD, like here. You might want to look into the query options -d in combination with -t for pacman’s -Q, to list packages installed as dependencies, but “Restrict or filter output to print only packages neither required nor optionally required by any currently installed package.”

Bonus cleanup pro-tip: alias pacorphans='sudo pacman -Qtdq | sudo pacman -Rns -' as explained in the wiki, mentioning makedepends in particular.

What kind of soulless psychopath leaves a window of this size unmaximized is the real question here. Also, a horizontal scrollbar in the main section, able to scroll maybe 8 pixels total to see some more of the glorious empty padding, could have been a nice touch as a consequence of the “unintended” window size.