Fix action on password required form (#269)

Author: helenb

tbx/project_styleguide/templates/patterns/pages/wagtail/password_required.html

@@ -18,7 +18,7 @@
             <p class="heading heading--four">Please enter the password to proceed.</p>
         </div>
 
-        <form action="#" method="post"  class="grid__form form">
+        <form action="{{ action_url }}" method="post"  class="grid__form form">
             {% csrf_token %}
 
             {{ form.non_field_errors }}