Simplify optimism divisor.
Passed STC:
LLR: 2.97 (-2.94,2.94) <-1.75,0.25>
Total: 139360 W: 36143 L: 36033 D: 67184
Ptnml(0-2): 436, 16456, 35778, 16582, 428
https://tests.stockfishchess.org/tests/view/66fc49c786d5ee47d953b94e
Passed LTC:
LLR: 2.95 (-2.94,2.94) <-1.75,0.25>
Total: 257748 W: 65163 L: 65184 D: 127401
Ptnml(0-2): 173, 28471, 71611, 28442, 177
https://tests.stockfishchess.org/tests/view/66ff01ae86d5ee47d953bb54
Passed LTC against rebased version:
LLR: 2.94 (-2.94,2.94) <-1.75,0.25>
Total: 53610 W: 13691 L: 13501 D: 26418
Ptnml(0-2): 52, 5942, 14605, 6176, 30
https://tests.stockfishchess.org/tests/view/670a9c5c86d5ee47d953c231
closes https://github.com/official-stockfish/Stockfish/pull/5633
Bench: 1282078