Editorial: add a missing quotation mark

Author: mathiasbynens

source

@@ -26002,7 +26002,7 @@ document.body.appendChild(wbr);</code></pre>
 
    <dt><dfn data-x="preload mode">mode</dfn>
    <dd>A <span data-x="concept-request-mode">request mode</span>, either
-   <code data-x="">same-origin</code>", "<code data-x="">cors</code>", or
+   "<code data-x="">same-origin</code>", "<code data-x="">cors</code>", or
    "<code data-x="">no-cors</code>"
 
    <dt><dfn data-x="preload credentials mode">credentials mode</dfn>