Remove useless button.

biscuit/core/templates/registration/login.html

@@ -20,8 +20,5 @@
   <button type="submit" class="btn btn-dark">
     {% blocktrans %}Login{% endblocktrans %}
   </button>  
-  <button type="hidden" class="btn btn-dark">
-    {{ next }}
-  </button>
  </form>
 {% endblock %}