Add missing quotation mark (#4277)

Fixing code issue in F24

Author: jschfflr

techniques/failures/F24.html

@@ -20,7 +20,7 @@ <h3>Specifying only background color with CSS</h3>
                the example fails the Success Criterion.</p>
 
 <pre xml:space="preserve"><code class="language-html">&lt;!doctype&gt;
-  &lt;html lang="en&gt;
+  &lt;html lang="en"&gt;
   &lt;head&gt;
     &lt;title&gt;Setting the canvas background&lt;/title&gt;
     &lt;style&gt;
@@ -104,4 +104,4 @@ <h3>Specifying foreground color of link text with CSS</h3>
             </li>
          </ul>
 
-   </section></body></html>
+   </section></body></html>