Remove job_token_policies_enabled setting

What does this MR do and why?

Remove the job_token_policies_enabled setting on top-level groups. Now job token policies are enabled by default for all groups.

References

Issue: #552125 (closed)

Screenshots or screen recordings

Before	After

How to set up and validate locally

1. Visit a top-level group's Settings > CI/CD > General pipelines page and verify the Enable fine-grained permissions for CI/CD job tokens setting is gone
2. Visit within the group a project's Settings > CI/CD > Job token permissions page and verify a Job token permissions column is displayed along with an edit button

MR acceptance checklist

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