Automatic merge of gitlab-org/gitlab-ce master

app/assets/stylesheets/framework/system_messages.scss

@@ -14,6 +14,7 @@
     @include str-truncated(100%);
     margin-top: -1px;
     margin-bottom: 0;
+    font-size: $gl-font-size-small;
   }
 }
 

app/assets/stylesheets/framework/variables.scss

@@ -289,7 +289,6 @@ $gl-line-height: 16px;
 $gl-line-height-24: 24px;
 $gl-line-height-14: 14px;
 
-$system-header-height: 35px;
 $issue-box-upcoming-bg: #8f8f8f;
 $pages-group-name-color: #4c4e54;
 

changelogs/unreleased/59131-set-the-size-of-instance-system-message-text-12px.yml

+---
+title: Update system message banner font size to 12px
+merge_request: 26293
+author:
+type: changed