Close HTML tag.

Fixup against 0903c9cc.

wiki/src/misc/unsafe_browser_warning.html

@@ -21,6 +21,7 @@ instead.</p>
 
     <p>Choose a website that is common in your location, for example a search
     engine or news site.</p>
+</li>
 
 <li>You should be redirected to the captive portal instead of the
 website.</li>