Remove `troubleshoot/pages` from admin tool or fix them

There's a https://frontend.gutools.co.uk/troubleshoot/pages endpoint in the admin tool

Currently, when we click test, it is failing to get the loadbalancer url

Is this endpoint used? If not, we can remove all the relevant code, otherwise fix the error.

Start at the admin tool's /troubleshoot/pages endpoint and reproduce the failing test that cannot obtain the loadbalancer URL. Determine whether the endpoint is used; done means either removing all relevant code or fixing the error so the test works.

Written by the indexing model from the issue text.