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_agreement.py

@@ -141,7 +141,7 @@ def test_unknown_gps_and_trusts_are_redirected(
     ),
 ))
 def test_download_service_agreement(
-    logged_in_client,
+    client_request,
     mocker,
     mock_get_service_organisation,
     crown,
@@ -160,11 +160,12 @@ def test_download_service_agreement(
         return_value=MockS3Object(b'foo')
     )
 
-    response = logged_in_client.get(url_for(
+    response = client_request.get(url_for(
         'main.service_download_agreement',
         service_id=SERVICE_ONE_ID,
+        _expected_status=expected_status,
+        _raw_respons=True,
     ))
-    assert response.status_code == expected_status
 
     if expected_file_served:
         assert response.get_data() == b'foo'