fix: prevent horizontal overflow on Look and Feel page, p=#10980

Author: nrysk

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

@@ -544,6 +544,12 @@ groupbox h2 {
   }
 }
 
+@media (max-width: 1320px) {
+  #zenLayoutList {
+    flex-wrap: wrap;
+  }
+}
+
 /* Disable mozilla's settings */
 
 #dataCollectionCategory,