Remove extra tags from csrf-demo.html (#418)

Author: dr-rompecabezas

example/example/templates/csrf-demo.html

@@ -26,11 +26,10 @@
       <input id="id_number"
              name="number"
              type="text"
-             placeholder=""></input>
+             placeholder="">
       <button type="submit">
         Check if odd
       </button>
-    </p>
     </form>
   </section>
   <section>