Tell people they can close tab once email auth’d

We’ve seen people come back to this page once signed in and be confused what it’s for and how they get back to Notify.

The best way to avoid confusion is (we think) getting people to close this tab.

app/templates/views/two-factor-email.html

@@ -10,7 +10,8 @@
 <div class="grid-row">
   <div class="column-two-thirds">
     <h1 class="heading-large">{{ title }}</h1>
-    <p> We’ve sent you an email with your login link</p>
+    <p>We’ve emailed you a link to sign in to Notify.</p>
+    <p>Clicking the link will open Notify in a new browser window, so you can close this one.</p>
     {{ page_footer(
       secondary_link=url_for('main.email_not_received'),
       secondary_link_text='Not received an email?'
@@ -18,4 +19,4 @@
   </div>
 </div>
 
-{% endblock %}
+{% endblock %}