[gnome-software/wip/exalm/upgrade-gradient] style: Simplify default background on upgrade banner

[Alexander Mikhaylenko <alexm src gnome org>]

commit 258374b2fb15153b4a44656a4e6c58782de69c16
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Wed Nov 10 17:55:59 2021 +0500

    style: Simplify default background on upgrade banner
    
    Use a solid color instead of a gradient, make sure it works with dark
    variant.

 src/style.css | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/style.css b/src/style.css
index c2835494b..90622fcb1 100644
--- a/src/style.css
+++ b/src/style.css
@@ -300,7 +300,7 @@ star-image {
 }
 
 .upgrade-banner-background {
-       background: linear-gradient(180deg, shade(@theme_bg_color, 1.0) 0%, shade(@theme_bg_color, 0.9) 100%);
+       background: alpha(currentColor, .05);
        color: @theme_fg_color;
        border-bottom: 1px solid @borders;
 }