[codex] skip approved PRs in stale review reminders

[redreceipt]

Summary

This updates the stale review reminder filter so PRs with GitHub's aggregate reviewDecision of APPROVED are excluded, even when GitHub still has leftover open review requests.

Root cause: the Slack job grouped any open reviewRequests as waiting-for-review work after checks passed. That let approved PRs like ApollosProject/apollos-shovel#1479 appear in the reminder because one requested reviewer was still pending after another reviewer had already approved it.

To Test

• source .venv-ci/bin/activate && python -m unittest discover -s tests -p 'test_*.py'
• source .venv-ci/bin/activate && ruff check .
• source .venv-ci/bin/activate && mypy .
• git diff --check

Proof

• Full unit suite passed: 95 tests.
• Ruff passed.
• Mypy passed with only existing advisory notes.
• Diff whitespace check passed.
• Live GitHub state for ApollosProject/apollos-shovel#1479 confirmed the repro shape: reviewDecision: APPROVED, successful checks, and an open review request still present.