ci: expect BACKLOG_ISSUE_TOKEN in scheduled alert wiring checks (#7867)

#7847 routed schedule-failure alerting to rustfs/backlog by switching the
alert jobs' token to secrets.BACKLOG_ISSUE_TOKEN, but check_test_wiring.py
still asserts the literal 'github-token: ${{ secrets.GITHUB_TOKEN }}', so
Quick Checks fails on every open PR. Update the wiring assertions and the
self-test fixtures to the new literal.

Both `--self-test` (52 tests) and the full `validate()` pass locally.