Fix obsolete format traits.

They are to be removed from the language in the next rust upgrade.

components/script/dom/htmllinkelement.rs

@@ -133,7 +133,7 @@ impl<'a> PrivateHTMLLinkElementHelpers for JSRef<'a, HTMLLinkElement> {
                 let LayoutChan(ref layout_chan) = window.page().layout_chan;
                 layout_chan.send(Msg::LoadStylesheet(url));
             }
-            Err(e) => debug!("Parsing url {:s} failed: {}", href, e)
+            Err(e) => debug!("Parsing url {} failed: {}", href, e)
         }
     }
 }