Update Jitsu auth host variable to not include subpath by default

What does this MR do and why?

Previously, we were hitting the Jitsu endpoint with the /configurator sub-path.

This URL is only available when running the Jitsu docker image that combines both the server and configurator UI.

In production use cases, the Configurator UI can be a standalone service, or sometimes not used at all.

See https://jitsu.com/docs/deployment/deploy-with-docker for more details.

How to set up and validate locally

1. Set up the devkit and start it running. docker-compose up

2. In this branch, run rails c to open the rails console

3. Enable the feature flag

   Feature.enable(:cube_api_proxy)

4. Set the required application settings:

   The Jitsu attributes are set up when first configuring your jitsu instance.

   ApplicationSetting.current.update(jitsu_project_xid: 'XXXXXXXXXX', jitsu_host: 'http://localhost:8000', clickhouse_connection_string: 'http://test:test@clickhouse:8123', jitsu_administrator_email: 'XXXXXXX', jitsu_administrator_password: 'XXXXXXX')
   reload!

5. Find a project on the console: project = Project.find(PROJECT_ID)

6. Run ProductAnalytics::InitializeStackService.new(container: project).execute

7. Ensure that a sidekiq job was enqueued.

8. Check the project and make sure that the Jitsu key has been stored: project.jitsu_key

9. In the Jitsu configurator, ensure that a new API key (with the project ID) has been created, along with a new associated connection to a clickhouse destination.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.