GTK3: pull upstream theme changes for 3.24.20

src/themes/Kali/sass/gtk-sass/upstream/_common.scss

@@ -4610,6 +4610,8 @@ decoration {
 
   .popup & { box-shadow: none; }
 
+  .csd & { background-color: black; } // transparent makes gtk3 leak light on the corners #2537
+
   // server-side decorations as used by mutter
   .ssd & { box-shadow: 0 0 0 1px $_wm_border; } //just doing borders, wm draws actual shadows
 
@@ -4640,10 +4642,6 @@ decoration {
 
     &:backdrop { box-shadow: inset 0 0 0 3px $backdrop_bg_color, inset 0 1px $top_hilight; }
   }
-
-  window.csd & {
-   background: black; /* transparent makes gtk3 leak light on the corners #2537 */
-  }
 }
 
 // Window Close button

src/themes/Kali/sass/gtk-sass/upstream/sync.sh

@@ -4,7 +4,7 @@ GREEN='\033[0;32m'
 YELLOW='\033[0;33m'
 RESET='\033[0m'
 
-VERSION=3.24.17
+VERSION=3.24.20
 
 echo
 echo -e " $YELLOW[ i ]$RESET Upstream version $VERSION"