Tweak futility pruning for extinction variants

Tweak futility pruning for extinction variants

extinction STC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 312 W: 196 L: 96 D: 20
http://www.variantfishtest.org:6543/tests/view/5f0ac6906e23db104fb88d83

extinction LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 491 W: 258 L: 162 D: 71
http://www.variantfishtest.org:6543/tests/view/5f0af0ff6e23db104fb88d92

threekings STC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 250 W: 89 L: 23 D: 138
http://www.variantfishtest.org:6543/tests/view/5f0ac6ac6e23db104fb88d86

threekings LTC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 179 W: 71 L: 9 D: 99
http://www.variantfishtest.org:6543/tests/view/5f0af0f46e23db104fb88d90

kinglet STC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 735 W: 373 L: 271 D: 91
http://www.variantfishtest.org:6543/tests/view/5f0af14f6e23db104fb88d94