Stop using logged_in_client fixture

We have a `client_request` fixture which does a bunch of useful stuff
like:
- checking the status code of the response
- returning a `BeautifulSoup` object

Lots of our tests still use an older fixture called `logged_in_client`.
This is not as good because:
- it returns a raw `Response` object
- doesn’t do the additional checks
- means our tests contain a lot of repetetive boilerplate like `page = BeautifulSoup(response.data.decode('utf-8'), 'html.parser')`

This commit converts all the tests using `logged_in_client` to:
use `client_request` instead.

tests/app/main/views/test_conversation.py

@@ -175,7 +175,7 @@ def test_view_conversation(
 
 
 def test_view_conversation_updates(
-    logged_in_client,
+    client_request,
     mocker,
     fake_uuid,
     mock_get_inbound_sms_by_id_with_no_messages,
@@ -191,13 +191,12 @@ def test_view_conversation_updates(
         return_value={'messages': 'foo'}
     )
 
-    response = logged_in_client.get(url_for(
+    response = client_request.get_response(
         'main.conversation_updates',
         service_id=SERVICE_ONE_ID,
         notification_id=fake_uuid,
-    ))
+    )
 
-    assert response.status_code == 200
     assert json.loads(response.get_data(as_text=True)) == {'messages': 'foo'}
 
     mock_get_partials.assert_called_once_with(SERVICE_ONE_ID, '07123 456789')