Stick email status to bottom of screen

We’ve moved away from using the expand/collapse pattern on the page
where you click ‘send’. Instead we’re putting the send button in the
sticky footer.

So it’s a bit jarring to still have the expand/collapse on the page you
see after you’ve sent an email. This commit replaces it with the sticky
footer as well.

This is only relevant for emails because:

1. Text messages are generally short enough to fit on the screen
2. We don’t show the status of letters because they don’t really change

app/main/views/notifications.py

@@ -65,6 +65,7 @@ def view_notification(service_id, notification_id):
             notification_id=notification_id,
             filetype='png',
         ),
+        expand_emails=True,
         page_count=page_count,
         show_recipient=True,
         redact_missing_personalisation=True,