widgets: remove redundant selector
widgets: remove redundant selector

We theme all frames now.

rgcjonas/adwaita-semidark,rgcjonas/adwaita-semidark,DoctorJellyface/gnome-themes-standard,ChrisCummins/gnome-themes-standard,cosimoc/gnome-themes-standard,Distrotech/gnome-themes-standard,cosimoc/gnome-themes-standard,DoctorJellyface/gnome-themes-standard,magcius/gnome-themes-standard,cosimoc/gnome-themes-standard,Distrotech/gnome-themes-standard,ChrisCummins/gnome-themes-standard,rgcjonas/adwaita-semidark,rgcjonas/adwaita-semidark,ChrisCummins/gnome-themes-standard,cosimoc/gnome-themes-standard,ChrisCummins/gnome-themes-standard,ChrisCummins/gnome-themes-standard,magcius/gnome-themes-standard,magcius/gnome-themes-standard