Make it clearer what Notify is for from homepage

Uses some graphic design to communicate what Notify is:

- for sending messages to lots of people
- messages can be personalised

app/templates/views/register.html

@@ -11,9 +11,6 @@ Create an account – GOV.UK Notify
 <div class="grid-row">
   <div class="column-two-thirds">
     <h1 class="heading-large">Create an account</h1>
-
-    <p>If you’ve used GOV.UK Notify before, <a href="{{ url_for('.sign_in') }}">sign in to your account</a></p>
-
     <form method="post" autocomplete="nope">
       {{ textbox(form.name, width='3-4') }}
       {{ textbox(form.email_address, hint="Must be from a central government organisation", width='3-4', safe_error_message=True) }}