[libadwaita/wip/exalm/sidebars: 2/4] Revert "demo: Stop overriding sidebar styles"

[Alexander Mikhaylenko <alexm src gnome org>]

commit a63b67a39c49442e2dc4d5da19d0f6be3fdeb373
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Sun Oct 24 04:17:36 2021 +0500

    Revert "demo: Stop overriding sidebar styles"
    
    This reverts commit d72a94fbea014ee79cef9df050679411321a2e41.

 demo/style.css | 9 +++++++++
 1 file changed, 9 insertions(+)
---
diff --git a/demo/style.css b/demo/style.css
index c294ce7c..667cadf8 100644
--- a/demo/style.css
+++ b/demo/style.css
@@ -1,3 +1,12 @@
+stacksidebar {
+  border-left-width: 0px;
+  border-right-width: 0px;
+}
+
+stacksidebar.background list {
+  background: @theme_bg_color;
+}
+
 carousel.vertical .carousel-icon {
   -gtk-icon-transform: rotate(90deg);
 }