Re-enable API benchmark script in CI

The api-benchmark-script was commented out in September 2024 during
the Python-to-SQL migration (commit 63c553e0). Now that the PostgREST
migration is complete and all smoke tests have been re-enabled, the
benchmark should also run again.

This generates request_process_times.log which is needed by the
benchmark-results-collector downstream job.

Also adds the missing YAML anchor (&api-benchmark-script) to the
script definition so it can be referenced.

🤖 Generated with [Claude Code](https://claude.com/claude-code

)

Co-Authored-By: Claude <noreply@anthropic.com>