[css-font-loading-3][editorial] Fixed Bikeshed warning

Author: SebastianZ

css-font-loading-3/Overview.bs

@@ -16,6 +16,7 @@ Link Defaults: css-fonts-4 (descriptor) src, dom (interface) Event
 Ignored Terms: EventHandler, InvalidModificationError, WorkerGlobalScope, Document, add(), src
 WPT Path Prefix: css/css-font-loading/
 WPT Display: closed
+Ignore MDN Failure: dom-fontface-variant
 </pre>
 
 <pre class="link-defaults">