Prepare outbound token UI for deprecation

What does this MR do and why?

This changes the UI for the outbound CI access token to announce the eventual deprecation of the feature. This is behind the frozen_outbound_job_token_scopes feature flag.

#395708 (closed)

Screenshots or screen recordings

Before	After

The feature can no longer be enabled once disabled

Screen_Recording_2023-04-24_at_13.16.33

How to set up and validate locally

1. Enable the frozen_outbound_job_token_scopes feature flag bundle exec rails c && echo "Feature.enable(:frozen_outbound_job_token_scopes)"
2. Go to any project -> Settings -> CI/CD -> Job Token
3. Verify that the Limit CI_JOB_TOKEN section is disabled

If you want to test you can't enable the feature again once it has been disabled

1. Disable the frozen_outbound_job_token_scopes feature flag bundle exec rails c && echo "Feature.disable(:frozen_outbound_job_token_scopes)"
2. Go to any project -> Settings -> CI/CD -> Job Token
3. Enable the Limit CI_JOB_TOKEN toggle
4. Reenable the feature flag
5. Go back to the Limit CI_JOB_TOKEN section and disable the toggle and try to enable it

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.