[gtk: 1/3] Adwaita: Remove a shadow-type leftover

[Matthias Clasen <matthiasc src gnome org>]

commit ef837f04151d58a1f7d8bbbf0db5d80549bd6777
Author: nana-4 <hnmaigo gmail com>
Date:   Tue Aug 25 21:12:35 2020 +0900

    Adwaita: Remove a shadow-type leftover
    
    After commit edae2a8dc500b7af29928e5eb6dfc305726ce6e0, frames always
    draw frames. So, remove the unused frame.flat styling.

 gtk/theme/Adwaita/_common.scss | 2 --
 1 file changed, 2 deletions(-)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 8ab52c8010..64db0790fb 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -3010,8 +3010,6 @@ frame,
   padding: 0;
   border-radius: 0;
   border: 1px solid $borders_color;
-
-  &.flat { border-style: none; }
 }
 
 actionbar > revealer >  box {