Change the finder-api healthcheck URL
Change the finder-api healthcheck URL

This should be deployed relatively closely to the time that
[finder-api release_46](https://github.com/alphagov/finder-api/releases/tag/release_46)
is deployed to Production.

In [finders-api@2258741](https://github.com/alphagov/finder-api/commit/2258741)
the schema URL changed which means that as soon as that commit is
deployed, the healthcheck will start failing.

```
ssharpe@preview-backend-1:~$ curl -sI http://localhost:3063/finders/cma-cases/schema.json | grep Status
Status: 200 OK
ssharpe@preview-backend-1:~$ curl -sI http://localhost:3063/cma-cases.json | grep Status
Status: 404 Not Found
```

alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet,alphagov/govuk-puppet