[gtk/wip/jimmac/no-inner-shadow-sidebars] Adwaita: no 3d shadow for pressed sidebar

[Jakub Steiner <jimmac src gnome org>]

commit 62e0c0de59550199b85b27f9940b11d0a7ab1c03
Author: Jakub Steiner <jimmac gmail com>
Date:   Mon Dec 7 14:19:24 2020 +0100

    Adwaita: no 3d shadow for pressed sidebar
    
    Fixes https://gitlab.gnome.org/GNOME/gtk/-/issues/3413

 gtk/theme/Adwaita/_common.scss | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/gtk/theme/Adwaita/_common.scss b/gtk/theme/Adwaita/_common.scss
index 5d60753d91..ea5df7a045 100644
--- a/gtk/theme/Adwaita/_common.scss
+++ b/gtk/theme/Adwaita/_common.scss
@@ -3588,6 +3588,9 @@ stacksidebar {
       background-color: $selected_bg_color;
       color: $selected_fg_color;
     }
+    &.activatable:active, &.activatable:selected:active {
+      box-shadow: none; // #3413
+    }
   }
 }