[gimp] themes: better styling for background dialog.

[Jehan <jehanp src gnome org>]

commit e916e93c1d8a928344c497e6deba1bc16f4e3f20
Author: Jehan <jehan girinstud io>
Date:   Sun Aug 21 12:39:21 2022 +0200

    themes: better styling for background dialog.
    
    This linear gradient really doesn't render any feeling of "background"
    IMO. I only initially implemented it this way because the underlying
    theme seemed to use such gradient effect on headerbar for background
    dialogs, so I wanted to test this.
    
    Anyway simply using the "disabled" color seem to work well. After all,
    the semantic is similar too (if it's in the background, a dialog can be
    considered inactive in some way). In any case, the meaning definitely
    comes across now.

 themes/Default/common.css | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
---
diff --git a/themes/Default/common.css b/themes/Default/common.css
index cef7d8216a..eb938ccc79 100644
--- a/themes/Default/common.css
+++ b/themes/Default/common.css
@@ -364,8 +364,8 @@ headerbar {
   background-image: none;
 }
 
-headerbar:backdrop {
-  background-image: linear-gradient(to top, @widget-bg-color, @extreme-bg-color);
+headerbar:backdrop * {
+  color: @disabled-fg-color;
 }
 
 /* GtkListBox widgets */