Stop exposing MR refs in favor of persistent pipeline refs

What does this MR do?

Exposing MR refs to runner causes failed to find ref error when the ref is cleaned up in a repository. Since we introduced a persistent ref !17043 (merged), we don't need to expose the refs anymore. So we stop exposing it when persistent ref is enabled.

Close #35140 (closed) #35918 (closed)

Manual QA

Case: When depend_on_persistent_pipeline_ref feature flag is enabled

• Event: When a job is enqueued and runner uses a shell executor.
• Expectation: The runner fetches a persistent ref and the job succeeds.
• Result: ✔

Case: When depend_on_persistent_pipeline_ref feature flag is disabled

• Event: When a job is enqueued and runner uses a shell executor.
• Expectation: The runner fetches a MR ref and the job succeeds.
• Result: ✔

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team