Actually allow configuring cloud_connector.base_url from config file

What does this MR do and why?

Actually allow configuring cloud_connector.base_url from config file

It seems this code in 1_settings.rb is almost correct for allowing us to use config/gitlab.yml to configure the cloud_connector URL. We prefer to use config/gitlab.yml per https://docs.gitlab.com/ee/development/architecture.html#adding-a-new-setting-in-gitlab-rails . This change should be a no-op in staging and production where we are presumably not setting this but relying on the default and the environment variable for staging

Aside from this being our preferred convention now this was also helpful locally as this setting is currently how we configure the Duo Workflow Service URL. Longer term that probably doesn't make sense to change this locally and we should just have a specific setting for that and we have this issue for that followup work #478660 .

MR acceptance checklist

Please evaluate this MR against the MR acceptance checklist. It helps you analyze changes to reduce risks in quality, performance, reliability, security, and maintainability.

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.