test_checkpoint_scrub_evict_config.test_mode(auto) introduced by WT-18005 fails intermittently in CI
with "AssertionError: 0 not greater than 0 : checkpoint_scrub_eviction=auto should scrub eligible pages, stat=0" on cache_write_restore_scrub_checkpoint. Evergreen failure patch

In auto mode, __sync_scrub_checkpoint_enabled can silently behaves as off and the counter stays at zero. As we already test both scrub eviction explicitly on and off, we can drop the auto scenario so the test no longer depends on the scrub heuristic. This is a similar failure to WT-18351.