Background color of private list-items updated (#20630)

A minor color update on the dashboard. This PR simply changes the background from hard-coded light yellow to the theme colors (var).

web_src/less/_base.less

@@ -123,6 +123,7 @@
   --color-text-light-3: #a0a0a0;
   --color-box-header: #f7f7f7;
   --color-box-body: #ffffff;
+  --color-box-body-highlight: #f8f8f8;
   --color-footer: #ffffff;
   --color-timeline: #ececec;
   --color-input-text: #212121;

web_src/less/_dashboard.less

@@ -165,7 +165,7 @@
         }
 
         &.private {
-          background-color: #fcf8e9;
+          background-color: var(--color-box-body-highlight);
         }
 
         .repo-list-link {

web_src/less/themes/theme-arc-green.less

@@ -95,6 +95,7 @@
   --color-body: #383c4a;
   --color-box-header: #404652;
   --color-box-body: #303440;
+  --color-box-body-highlight: #353945;
   --color-text-dark: #dbe0ea;
   --color-text: #bbc0ca;
   --color-text-light: #a6aab5;
@@ -150,10 +151,6 @@
   color: #fff;
 }
 
-.feeds .list ul li.private {
-  background: #353945;
-}
-
 .ui.red.label,
 .ui.red.labels .label {
   background-color: #7d3434 !important;