Update anchor to job artifacts cleaning documentation

What does this MR do and why?

The "When job artifacts are deleted" header was removed from doc/ci/pipelines/job_artifacts.md in commit f3244415, after GitLab 15.10 and before GitLab 16.0.

Update link to new location.

For tracking:

• The page was moved in Split and move job artifacts page (!116633 - merged)
• The header was renamed in CTRT cleanup of artifacts page (!115818 - merged)

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