Tweak probcut margin for extinction variants

Tweak probcut margin for extinction variants

shatranj STC
LLR: 2.95 (-2.94,2.94) [0.00,10.00]
Total: 1753 W: 212 L: 146 D: 1395
http://www.variantfishtest.org:6543/tests/view/601473246e23db669974e64a

shatranj LTC
LLR: 2.97 (-2.94,2.94) [-10.00,5.00]
Total: 2653 W: 205 L: 173 D: 2275
http://www.variantfishtest.org:6543/tests/view/60148af66e23db669974e65e

horde LTC
LLR: 2.96 (-2.94,2.94) [-10.00,5.00]
Total: 1249 W: 648 L: 589 D: 12
http://www.variantfishtest.org:6543/tests/view/60148b226e23db669974e660