Enable shallow depth pruning for horde chess

Enable shallow depth pruning for horde chess

horde STC
LLR: 3.36 (-2.94,2.94) [0.00,10.00]
Total: 517 W: 320 L: 196 D: 1
http://35.161.250.236:6543/tests/view/5c2286ad6e23db247289560e

horde LTC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 321 W: 213 L: 106 D: 2
http://35.161.250.236:6543/tests/view/5c22a79f6e23db2472895618

giveaway STC
LLR: 3.00 (-2.94,2.94) [-10.00,5.00]
Total: 5940 W: 1928 L: 1914 D: 2098
http://35.161.250.236:6543/tests/view/5c22a7dc6e23db247289561c

giveaway LTC
LLR: 2.96 (-2.94,2.94) [-10.00,5.00]
Total: 4212 W: 1345 L: 1321 D: 1546
http://35.161.250.236:6543/tests/view/5c22aa416e23db2472895622