Merge branch '332207-lines-between-stages-in-darkmode' into 'master'

Fix CSS for MR widget for dark mode

See merge request gitlab-org/gitlab!62783

app/assets/stylesheets/page_bundles/pipelines.scss

@@ -116,7 +116,7 @@
         position: absolute;
         right: -7px;
         top: 11px;
-        border-bottom: 2px solid $border-color;
+        border-bottom: 2px solid var(--border-color, $border-color);
       }
     }