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_two_factor.py

@@ -487,11 +487,10 @@ def test_two_factor_email_link_when_user_is_locked_out(
 
 
 def test_two_factor_email_link_used_when_user_already_logged_in(
-    logged_in_client,
+    client_request,
     valid_token
 ):
-    response = logged_in_client.post(
-        url_for_endpoint_with_token('main.two_factor_email', token=valid_token)
+    client_request.post_url(
+        url_for_endpoint_with_token('main.two_factor_email', token=valid_token),
+        _expected_redirect=url_for('main.show_accounts_or_dashboard', _external=True),
     )
-    assert response.status_code == 302
-    assert response.location == url_for('main.show_accounts_or_dashboard', _external=True)