Adwaita: Update treeview rubberband styling

Adapt to the changes in the previous commit.

gtk/theme/Adwaita/_common.scss

@@ -1274,7 +1274,7 @@ treeview.view {
   border-left-color: mix($fg_color, $base_color, 50%); // this is actually the tree lines color,
   border-top-color: $bg_color;                         // while this is the grid lines color, better then nothing
 
-  &.rubberband { @extend rubberband; } // to avoid borders being overridden by the previously set props
+  & rubberband { @extend rubberband; } // to avoid borders being overridden by the previously set props
 
   &:selected { border-radius: 0; } // rest border radius in lists
 

gtk/theme/Adwaita/gtk-contained-dark.css

@@ -80,7 +80,7 @@ textview text,
 .rubberband,
 rubberband,
 flowbox rubberband,
-treeview.view.rubberband,
+treeview.view rubberband,
 .content-view rubberband {
   border: 1px solid #184472;
   background-color: rgba(24, 68, 114, 0.2); }

gtk/theme/Adwaita/gtk-contained.css

@@ -80,7 +80,7 @@ textview text,
 .rubberband,
 rubberband,
 flowbox rubberband,
-treeview.view.rubberband,
+treeview.view rubberband,
 .content-view rubberband {
   border: 1px solid #2a76c6;
   background-color: rgba(42, 118, 198, 0.2); }