[codex] Disable scheduled leaderboard post

[redreceipt]

Summary

• Comment out the scheduled Friday weekly leaderboard Slack post.
• Leave the debug runner path intact so DEBUG=true still posts the leaderboard manually.
• Update the existing scheduled-jobs test expectation to match the temporary disabled schedule.

Validation

• source venv/bin/activate && python -m unittest discover -s tests -p 'test_*.py'

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Note

Low Risk
Only comments out one cron-style Slack job and adjusts a test; no auth, data, or leaderboard logic changes.

Overview
Temporarily stops the automated Friday 4:00 PM (America/New_York) weekly leaderboard Slack post by commenting out its schedule registration in configure_scheduled_jobs. Other scheduled jobs are unchanged.

post_leaderboard is still invoked from run_debug_jobs when DEBUG=true, so manual/debug runs can still send the message. The scheduled-jobs unit test now expects the Friday leaderboard entry not to be registered.

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