Make benchmark-results-collector trigger manual

The api-benchmark-script is currently commented out in
e2e_benchmark_on_postgrest, so request_process_times.log is not
generated. This causes the benchmark-results-collector job to fail
with FileNotFoundError.

Setting the trigger to manual until benchmarks are re-enabled.

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

)

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