Update 'index.html'

replaced the latest </span> tag with </code>

index.html

@@ -167,7 +167,7 @@
                 If ALIAS isn't supported, use A & AAAA instead:<br>
                 <code class="code">A 217.197.91.145</code><br>
                 <code class="code">AAAA 2001:67c:1401:20f0::1</code><br>
-                + <code class="code">TXT</span> as above
+                + <code class="code">TXT</code> as above
               </p>
             </div>
           </div>