Simplify history bonus
After we recently added the disallowance for negative bonuses, it is no
longer necessary to keep the max comparison in the previous step.
Passed STC:
LLR: 2.93 (-2.94,2.94) <-1.75,0.25>
Total: 72000 W: 18820 L: 18637 D: 34543
Ptnml(0-2): 267, 8489, 18276, 8730, 238
https://tests.stockfishchess.org/tests/view/66ce132cbf8c9d8780fdabe7
Passed LTC:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 67452 W: 17136 L: 16961 D: 33355
Ptnml(0-2): 35, 7489, 18519, 7632, 51
https://tests.stockfishchess.org/tests/view/66cf6ad49de3e7f9b33d1010
closes https://github.com/official-stockfish/Stockfish/pull/5554
Bench: 1147012