gh-9836: Finish the MAR signing workflow (gh-13216)

src/browser/themes/shared/preferences/zen-preferences.css

@@ -504,6 +504,7 @@ groupbox h2 {
 #setting-control-sidebarChatbotFieldset,
 #aiControlsDescription,
 #category-ai-features,
+#setting-control-supportFirefox,
 .mission-message,
 html|setting-group[data-subcategory="layout"] {
   display: none !important;