Remove essentially unused code

Remove essentially unused code

this was added recently as part of a larger commit, but only changes eval of positions at MAX_PLY depth a little. Can be safely removed:

passed STC:
LLR: 2.95 (-2.94,2.94) [-3.00,1.00]
Total: 7424 W: 1640 L: 1492 D: 4292
http://tests.stockfishchess.org/html/live_elo.html?5ba3bcbe0ebc592cf27677ff

passed LTC:
LLR: 2.96 (-2.94,2.94) [-3.00,1.00]
Total: 73554 W: 12028 L: 11990 D: 49536
http://tests.stockfishchess.org/html/live_elo.html?5ba397ee0ebc592cf2767556

unchanged Bench: 4248710