Tweak scaling of passed pawn evaluation

Tweak scaling of passed pawn evaluation

shatranj STC
LLR: 2.97 (-2.94,2.94) [0.00,10.00]
Total: 4787 W: 590 L: 504 D: 3693
http://35.161.250.236:6543/tests/view/5c8ccad36e23db76ed25260d

shatranj LTC
LLR: 15.68 (-2.94,2.94) [0.00,10.00]
Total: 15959 W: 1537 L: 1169 D: 13253
http://35.161.250.236:6543/tests/view/5c8d69876e23db76ed252610

ELO: 6.25 +-6.4 (95%) LOS: 97.3%
Total: 2000 W: 194 L: 158 D: 1648
http://35.161.250.236:6543/tests/view/5cab9f0d6e23db76ed2526c0

kinglet LTC
ELO: -9.56 +-14.2 (95%) LOS: 9.4%
Total: 2000 W: 846 L: 901 D: 253
http://35.161.250.236:6543/tests/view/5cab9eed6e23db76ed2526be