update conftest and tests to contain accurate test data

specifically, we identify inbound vs outbound by presence of
"notify_number", so ensure that test content actually contains that
field

app/main/views/conversation.py

@@ -64,7 +64,7 @@ def get_sms_thread(service_id, user_number):
     ), key=lambda notification: notification['created_at']):
 
         is_inbound = ('notify_number' in notification)
-        redact_personalisation = notification.get('template', {}).get('redact_personalisation', False)
+        redact_personalisation = not is_inbound and notification['template']['redact_personalisation']
 
         if redact_personalisation:
             notification['personalisation'] = {}